<PAGE>

                                                                  EXECUTION COPY
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                                                                   Exhibit 10.21


                         REGISTRATION RIGHTS AGREEMENT



                         Dated as of December 15, 1999
                                  by and among

                              Global Crossing Ltd.

                                      and

               Merrill Lynch, Pierce, Fenner & Smith Incorporated
                           Salomon Smith Barney Inc.
                              Goldman, Sachs & Co.
                             Chase Securities Inc.
                        Morgan Stanley Dean Witter & Co.
                            CIBC World Markets Corp.
              Donaldson, Lufkin & Jenrette Securities Corporation
                     Credit Suisse First Boston Corporation



================================================================================
<PAGE>

     This Registration Rights Agreement (this "Agreement") is made and entered
                                               ---------
into as of December 15, 1999, by and among Global Crossing Ltd., a Bermuda
company (the "Company"), and Merrill Lynch, Pierce, Fenner & Smith Incorporated,
              -------
Salomon Smith Barney Inc., Goldman, Sachs & Co., Chase Securities Inc., Morgan
Stanley Dean Witter & Co., CIBC World Markets Corp., Donaldson, Lufkin &
Jenrette Securities Corporation and Credit Suisse First Boston Corporation
(each, an "Initial Purchaser" and, collectively, the "Initial Purchasers"), each
           -----------------                          ------------------
of whom has agreed to purchase, severally and not jointly, an aggregate of
2,000,000 shares of the Company's 7% Cumulative Convertible Preferred Stock,
with the option to purchase up to an additional 600,000 shares of the Company's
7% Cumulative Convertible Preferred Stock, for the sole purpose of covering
over-allotments (collectively the "Preferred Stock") pursuant to the Purchase
                                   ---------------
Agreement (as defined below).

     This Agreement is made pursuant to the Purchase Agreement, dated as of
December 9, 1999 (the "Purchase Agreement"), by and among the Company and the
                       ------------------
Initial Purchasers.  In order to induce the Initial Purchasers to purchase the
Preferred Stock, the Company has agreed to provide the registration rights set
forth in this Agreement.  The execution and delivery of this Agreement is a
condition to the obligations of the Initial Purchasers to purchase the Preferred
Stock as set forth in the Purchase Agreement.

     The parties hereby agree as follows:

SECTION 1.  DEFINITIONS

     As used in this Agreement, the following capitalized terms shall have the
following meanings:

     Act:  The Securities Act of 1933, as amended.
     ---

     Affiliate:  As defined in Rule 144 of the Act.
     ---------

     Bye-laws:  The Bye-laws of the Company to be amended by the Company on or
     --------
prior to  the Closing Date, which will contain the terms of the Preferred Stock.

     Certificate of Designations:  The Certificate of Designations, to be
     ---------------------------
entered into by the Company governing the Preferred Stock, as such Certificate
of Designations is amended, modified or supplemented from time to time in
accordance with the terms thereof.

     Closing Date:  The date hereof.
     ------------

     Commission:  The Securities and Exchange Commission.
     ----------

     Common Stock:  The common stock, $0.01 par value, of the Company.
     ------------

     Dividend Payment Date:  As defined in the Certificate of Designations.
     ---------------------

     Effectiveness Deadline:  As defined in Section 3(a) hereof.
     ----------------------

                                       1
<PAGE>

     Exchange Act:  The Securities Exchange Act of 1934, as amended.
     ------------

     Filing Deadline:  As defined in Section 3(a) hereof.
     ---------------

     Holders:  As defined in Section 2 hereof.
     -------

     Indemnified Holder:  As defined in Section 8(a) hereof.
     ------------------

     Liquidation Preference:  As defined in the Certificate of Designations.
     ----------------------

     Preferred Stock:  As defined in the preamble hereof.
     ---------------

     Preferred Stock Shares:  The Common Stock or other securities which any
     ----------------------
Holder may acquire upon conversion of the Preferred Stock, together with any
other securities which such Holder may acquire on account of any such
securities, including, without limitation, as the result of any dividend or
other distribution on Common Stock or any split-up of such Common Stock as
provided for in the Certificate of Designations.

     Prospectus:  The prospectus included in a Registration Statement at the
     ----------
time such Registration Statement is declared effective, as amended or
supplemented by any prospectus supplement and by all other amendments thereto,
including post-effective amendments, and all material incorporated by reference
into such Prospectus.

     Recommencement Date: As defined in Section 6(b) hereof.
     -------------------

     Registrable Securities:  The Preferred Stock, Preferred Stock Shares and
     ----------------------
any other securities issued or issuable with respect to the Preferred Stock or
the Preferred Stock Shares by way of a stock dividend or stock split or in
connection with a combination of shares, recapitalization, merger, consolidation
or other reorganization; provided that a security ceases to be a Registrable
Security when it is no longer a Transfer Restricted Security.

     Registration Default:  As defined in Section 5 hereof.
     --------------------

     Registration Statement:  Any registration statement of the Company relating
     ----------------------
to the registration for resale of Registrable Securities pursuant to the Shelf
Registration Statement, (i) that is filed pursuant to the provisions of this
Agreement and (ii) including the Prospectus included therein, all amendments and
supplements thereto (including post-effective amendments) and all exhibits and
material incorporated by reference therein.

     Rule 144:  Rule 144 promulgated under the Act.
     --------

     Shelf Registration Statement:  As defined in Section 3 hereof.
     ----------------------------

     Special Dividends:  As defined in Section 5 hereof.
     -----------------

     Suspension Notice:  As defined in Section 6(b) hereof.
     -----------------

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<PAGE>

     Transfer Agent:  EquiServe.
     --------------

     Transfer Restricted Securities:  The Preferred Stock or Preferred Stock
     ------------------------------
Shares, until the earliest to occur of (a) the date on which such Preferred
Stock or Preferred Stock Shares, as applicable, is effectively registered under
the Act and disposed of in accordance with a Shelf Registration Statement, (b)
the date on which such Preferred Stock or Preferred Stock Shares, as applicable,
is distributed to the public pursuant to Rule 144 under the Act or (c) the date
on which such Preferred Stock or Preferred Stock Shares, as applicable, is
eligible for resale pursuant to Rule 144 without volume restrictions.

SECTION 2.  HOLDERS

     (x)  Registrable Securities.  The securities entitled to the benefits of
          ----------------------
this Agreement are the Registrable Securities.

     (y)  Holders of Registrable Securities.  A Person is deemed to be a holder
          ---------------------------------
of Registrable Securities (each, a "Holder") whenever such Person owns
Registrable Securities or has the right to acquire such Registrable Securities,
whether or not such acquisition has actually been effected and disregarding any
legal restrictions upon the exercise of such right.

SECTION 3.  SHELF REGISTRATION

     The Company shall:

     (x)  use its reasonable best efforts to cause to be filed with the
Commission as soon as practicable after the Closing Date, but in no event later
than 90 days after the Closing Date (the "Filing Deadline"), a shelf
                                          ---------------
registration statement pursuant to Rule 415 under the Act (the "Shelf
                                                                -----
Registration Statement") relating to all Registrable Securities, and
----------------------

     (y)  use its reasonable best efforts to cause such Shelf Registration
Statement to become effective on or prior to 90 days after the Filing Deadline
(such 90th day being referred to herein as the "Effectiveness Deadline").
                                                ----------------------

     The Company shall use its best efforts to keep any Shelf Registration
Statement required by this Section 3(a) continuously effective, supplemented and
amended as required by, and subject to the provisions of, Sections 6(a) and (b)
hereof to the extent necessary to ensure that it is available for sales of
Registrable Securities by the Holders thereof entitled to the benefit of this
Section 4(a), and to ensure that it conforms with the requirements of this
Agreement, the Act and the policies, rules and regulations of the Commission as
announced from time to time, for a period of at least two years (as extended
pursuant to Section 6(b)) following the date on which such Shelf Registration
Statement first becomes effective under the Act, or such shorter period as will
terminate when all Transfer Restricted Securities covered by such Registration
Statement have been sold pursuant thereto.

     (a)  Provision by Holders of Certain Information in Connection with the
          ------------------------------------------------------------------
Shelf Registration Statement.  No Holder of Registrable Securities may include
----------------------------
any of its Registrable

                                       3
<PAGE>

Securities in any Shelf Registration Statement pursuant to this Agreement unless
and until such Holder furnishes to the Company in writing,  within 20 days after
receipt of a request therefor,  the information  specified in Item 507 or 508 of
Regulation  S-K, as applicable,  of the Act for use in connection with any Shelf
Registration Statement or Prospectus or preliminary Prospectus included therein.
Each selling Holder agrees to promptly furnish additional  information  required
to be disclosed  in order to make the  information  previously  furnished to the
Company by such Holder not materially misleading.

SECTION 4.  BLACK OUT PERIOD

     During any consecutive 365 day period, the Company may suspend the
effectiveness of the Shelf Registration Statement for an aggregate period of not
more than 90 consecutive days if there is a possible acquisition or business
combination or other transaction, business development or event involving the
Company that may require disclosure in the Shelf Registration Statement and the
Company determines in the exercise of its reasonable judgment that such
disclosure is not in the best interests of the Company and its stockholders or
obtaining any financial statements relating to an acquisition or business
combination required to be included in the Shelf Registration Statement would be
impracticable. In such a case, the Company shall promptly notify Holders of the
suspension of the Shelf Registration Statement's effectiveness, provided that
such notice shall not require the Company to disclose the possible acquisition
or business combination or other transaction, business development or event if
the Company determines in good faith that such acquisition or business
combination or other transaction, business development or event should remain
confidential.  Upon the abandonment, consummation, or termination of the
possible acquisition or business combination or other transaction, business
development or event, or the availability of the required financial statements
with respect to a possible acquisition or business combination, the suspension
of the use of the Shelf Registration Statement pursuant to this Section 4 shall
cease and the Company shall promptly comply with Section 6(a)(ii) hereof and
notify the Holders that disposition of Registrable Securities may be resumed.

SECTION 5.  SPECIAL DIVIDENDS

     If (i) the Registration Statement required by this Agreement is not filed
with the Commission on or prior to the Filing Deadline, (ii) the Registration
Statement has not been declared effective by the Commission on or prior to the
Effectiveness Deadline, or (iii) the Registration Statement required by this
Agreement is filed and declared effective but shall thereafter cease to be
effective or fail to be usable for its intended purpose (except in the
circumstances specified in Section 4) without being succeeded immediately by a
post-effective amendment to such Registration Statement that cures such failure
and that is itself declared effective immediately (each such event referred to
in clauses (i) through (iii), a "Registration Default"), then the Company hereby
                                 --------------------
agrees to pay to each Holder of Registrable Securities affected thereby special
dividends ("Special Dividends") which will accrue and be payable semi-annually
            -----------------
on the Preferred Stock (or per such number of Preferred Stock Shares then
issuable upon exercise of or in respect of the Preferred Stock) in addition to
the stated dividends on the Preferred Stock (or per such number of Preferred
Stock Shares then issuable upon exercise of or

                                       4
<PAGE>

in respect of the Preferred  Stock),  as the case may be, from and including the
date such Registration  Default occurs to, but excluding,  the date on which (1)
the Shelf  Registration  Statement is filed,  in the case of (i) above,  (2) the
Shelf Registration  Statement is declared effective,  in the case of (ii) above,
or  (3)  a  post-  effective  amendment  to  the  Registration  Statement  or an
additional  Registration  Statement is filed that causes the Shelf  Registration
Statement to again be declared  effective  or made usable,  in the case of (iii)
above.  During the time that Special  Dividends are accruing  continuously,  the
rate of such Special  Dividends shall be 0.50% per annum during the first 90-day
period and shall increase by 0.25% per annum for each subsequent  90-day period,
but in no event  shall  such  rate  exceed  1.00%  per  annum  in the  aggregate
regardless  of the number of  Registration  Defaults.  If, after the cure of all
Registration  Defaults  then  in  effect,  there  is a  subsequent  Registration
Default,  the Special  Dividend rate for such  subsequent  Registration  Default
shall initially be 0.25%, regardless of the Special Dividend rate in effect with
respect  to any  prior  Registration  Default  at the  time of the  cure of such
Registration Default. All accrued Special Dividends shall be paid to the Holders
entitled  thereto,  in the manner  provided  for the payment of dividends as set
forth  in the  Bye-Laws.  All  obligations  of the  Company  set  forth  in this
paragraph that are outstanding  with respect to any Registrable  Security at the
time such security ceases to be a Registrable  Security shall survive until such
time as all such  obligations  with respect to such  Registrable  Security shall
have been satisfied in full.

SECTION 6.  REGISTRATION PROCEDURES

     In connection with the Shelf Registration Statement, the Company shall
comply with all the provisions of Section 6(a) below and shall use its best
efforts to effect such registration to permit the sale of the Transfer
Restricted Securities being sold in accordance with the intended method or
methods of distribution thereof (as indicated in the information furnished to
the Company pursuant to Section 3(b) hereof), and pursuant thereto the Company
will prepare and file with the Commission a Registration Statement relating to
the registration on any appropriate form under the Act, which form shall be
available for the sale of the Transfer Restricted Securities in accordance with
the intended method or methods of distribution thereof within the time periods
and otherwise in accordance with the provisions hereof and pursuant thereto the
Company shall:

     (a)  General Provisions.
          ------------------

          (i)  except in the circumstances specified in Section 4, use its
     reasonable best efforts to keep such Registration Statement continuously
     effective and provide all requisite financial statements for the period
     specified in Section 3 of this Agreement.  Except in the circumstances
     specified in Section 4, upon the occurrence of any event that would cause
     any such Registration Statement or the Prospectus contained therein (A) to
     contain a material misstatement or omission or (B) not to be effective and
     usable for resale of Registrable Securities during the period required by
     this Agreement, the Company shall file promptly an appropriate amendment to
     such Registration Statement curing such defect, and, if Commission review
     is required, use its reasonable best efforts

                                       5
<PAGE>

     to cause such amendment to be declared effective as soon as reasonably
     practicable thereafter.

          (ii)  except in the circumstances specified in Section 4, prepare and
     file with the Commission such amendments and post-effective amendments to
     the applicable Registration Statement as may be necessary to keep such
     Registration Statement effective for the period set forth in Section 3
     hereof, or such shorter period as will terminate when all Registrable
     Securities covered by such Registration Statement have been sold or until
     such Registrable Securities no longer constitute Registrable Securities or
     are no longer outstanding; cause the Prospectus to be supplemented by any
     required Prospectus supplement, and as so supplemented to be filed pursuant
     to Rule 424 under the Act, and to comply fully with Rules 424, 430A and
     462, as applicable, under the Act in a timely manner; and comply with the
     provisions of the Act with respect to the disposition of all securities
     covered by such Registration Statement during the applicable period in
     accordance with the intended method or methods of distribution by the
     sellers thereof set forth in such Registration Statement or supplement to
     the Prospectus;

          (iii)  advise the selling Holders promptly and, if requested by such
     Persons, confirm such advice in writing, (A) when the Prospectus or any
     Prospectus supplement or post-effective amendment has been filed, and, with
     respect to any applicable Registration Statement or any post-effective
     amendment thereto, when the same has become effective, (B) of any request
     by the Commission for amendments to the Registration Statement or
     amendments or supplements to the Prospectus or for additional information
     relating thereto, (C) of the issuance by the Commission of any stop order
     suspending the effectiveness of the Registration Statement under the Act or
     of the suspension by any state securities commission of the qualification
     of the Registrable Securities for offering or sale in any jurisdiction, or
     the initiation of any proceeding for any of the preceding purposes, or (D)
     except in the circumstances specified in Section 4, of the existence of any
     fact or the happening of any event that makes any statement of a material
     fact made in the Registration Statement, the Prospectus, any amendment or
     supplement thereto or any document incorporated by reference therein
     untrue, or that requires the making of any additions to or changes in the
     Registration Statement in order to make the statements therein not
     misleading, or that requires the making of any additions to or changes in
     the Prospectus in order to make the statements therein, in the light of the
     circumstances under which they were made, not misleading.  If at any time
     the Commission shall issue any stop order suspending the effectiveness of
     the Registration Statement, or any state securities commission or other
     regulatory authority shall issue an order suspending the qualification or
     exemption from qualification of the Registrable Securities under state
     securities or Blue Sky laws, the Company shall use its best efforts to
     obtain the withdrawal or lifting of such order at the earliest practicable
     time;

          (iv)  subject to Section 6(a)(i), if any fact or event contemplated by
     Section 6(a)(iii)(D) above shall exist or have occurred, prepare a
     supplement or post-effective amendment to the Registration Statement or
     related Prospectus or any document incorporated therein by reference or
     file any other required document so that, as thereafter

                                       6
<PAGE>

     delivered to the purchasers of Registrable Securities, the Prospectus will
     not contain an untrue statement of a material fact or omit to state any
     material fact necessary to make the statements therein, in the light of the
     circumstances under which they were made, not misleading;

          (v)  furnish to the Initial Purchasers and each selling Holder named
     in any Registration Statement or Prospectus in connection with such sale,
     if any, before filing with the Commission, copies of any Registration
     Statement or any Prospectus included therein or any amendments or
     supplements to any such Registration Statement or Prospectus (including all
     documents incorporated by reference, if requested by such person), which
     documents will be subject to the review and comment of such Holders in
     connection with such sale, if any, for a period of at least five Business
     Days, and the Company will not file any such Registration Statement or
     Prospectus or any amendment or supplement to any such Registration
     Statement or Prospectus (including all such documents incorporated by
     reference, if requested by such person) to which the selling Holders of the
     Registrable Securities covered by such Registration Statement in connection
     with such sale, if any, shall reasonably object within five Business Days
     after the receipt thereof.  A selling Holder shall be deemed to have
     reasonably objected to such filing if such Registration Statement,
     amendment, Prospectus or supplement, as applicable, as proposed to be
     filed, contains a material misstatement or omission or fails to comply with
     the applicable requirements of the Act;

          (vi)  promptly prior to the filing of any document that is to be
     incorporated by reference into a Registration Statement or Prospectus, if
     requested by any selling Holders within five Business Days after receipt of
     notification thereof from the Company, provide copies of such document to
     such selling Holders in connection with such sale, if any, make the
     Company's representatives available for discussion of such document and
     other customary due diligence matters, and include such information in such
     document prior to the filing thereof as such selling Holders may reasonably
     request;

          (vii)  make available at reasonable times for inspection by the
     selling Holders participating in any disposition pursuant to such
     Registration Statement and any attorney or accountant retained by such
     selling Holders, all financial and other records, pertinent corporate
     documents of the Company and cause the Company's officers, directors and
     employees to supply all information reasonably requested by any such
     selling Holder, attorney or accountant in connection with such Registration
     Statement or any post-effective amendment thereto subsequent to the filing
     thereof and prior to its effectiveness;

          (viii)  if requested by any selling Holders in connection with such
     sale, if any, promptly include in any Registration Statement or Prospectus,
     pursuant to a supplement or post-effective amendment if necessary, such
     information as such selling Holders may reasonably request to have included
     therein, including, without limitation, information relating to the "Plan
     of Distribution" of the Registrable Securities; and make all required
     filings of such Prospectus supplement or post-effective amendment as soon
     as practicable

                                       7
<PAGE>

     after the Company is notified of the matters to be included in such
     Prospectus supplement or post-effective amendment;

          (ix)  furnish to each selling Holder in connection with such sale, if
     any, without charge, at least one copy of the Registration Statement, as
     first filed with the Commission, and of each amendment thereto, including
     all documents incorporated by reference therein and all exhibits (including
     exhibits incorporated therein by reference);

          (x)  deliver to each selling Holder, without charge, as many copies of
     the Prospectus (including each preliminary prospectus) and any amendment or
     supplement thereto as such Persons reasonably may request; the Company
     hereby consents to the use (in accordance with law) of the Prospectus and
     any amendment or supplement thereto by each of the selling Holders in
     connection with the offering and the sale of the Registrable Securities
     covered by the Prospectus or any amendment or supplement thereto;

          (xi)  upon the request of any selling Holder, enter into such
     agreements (including underwriting agreements) and make such
     representations and warranties and take all such other actions in
     connection therewith in order to expedite or facilitate the disposition of
     the Registrable Securities pursuant to any applicable Registration
     Statement contemplated by this Agreement, all to such extent as may be
     reasonably acceptable to the Company and as may be reasonably requested by
     any Holder of Registrable Securities in connection with any sale or resale
     pursuant to any applicable Registration Statement contemplated by this
     Agreement and in such connection, the Company shall:

          (A) upon request of any selling Holder, furnish (or in the case of
       paragraphs (2) and (3), use its best efforts to cause to be furnished) to
       each selling Holder, upon the effectiveness of the Shelf Registration
       Statement:

               (1) a certificate, dated such date, signed on behalf of the
          Company by (x) the Chief Executive Officer, President or any Vice
          President and (y) a principal financial or accounting officer of the
          Company, confirming, as of the date thereof, the matters set forth in
          paragraph (e) of Section 6 of the Purchase Agreement and such other
          similar matters as the selling Holders may reasonably request;

               (2) opinions, dated such date, of counsel for the Company
          covering matters similar to those set forth in paragraphs (a), (b) and
          (c) of Section 6 of the Purchase Agreement and such other matters as
          the selling Holders may reasonably request, and in any event including
          a statement to the effect that certain such counsel has participated
          in conferences with officers and other representatives of the Company
          and representatives of the independent public accountants for the
          Company at which the contents of such Registration Statement and the
          related Prospectus were discussed, although such counsel has not
          independently verified the accuracy, completeness or fairness of such
          statements; and that such counsel

                                       8
<PAGE>

          advises that, on the basis of the foregoing, no facts came to such
          counsel's attention that caused such counsel to believe that the
          applicable Registration Statement, at the time such Registration
          Statement or any post-effective amendment thereto became effective
          contained an untrue statement of a material fact or omitted to state a
          material fact required to be stated therein or necessary to make the
          statements therein not misleading, or that the Prospectus contained in
          such Registration Statement as of its date contained an untrue
          statement of a material fact or omitted to state a material fact
          necessary in order to make the statements therein, in the light of the
          circumstances under which they were made, not misleading. Without
          limiting the foregoing, such counsel may state further that such
          counsel assumes no responsibility for, and has not independently
          verified, the accuracy, completeness or fairness of the financial
          statements, notes and schedules and other financial data included in
          any Registration Statement contemplated by this Agreement or the
          related Prospectus; and

               (3) a customary comfort letter, dated such date, from the
          Company's independent accountants, in the customary form and covering
          matters of the type customarily covered in comfort letters to
          underwriters in connection with underwritten offerings, and affirming
          the matters set forth in the comfort letters delivered pursuant to
          Section 6(f) of the Purchase Agreement; and

          (B) deliver such other documents and certificates as may be reasonably
       requested by the selling Holders to evidence compliance with clause (A)
       above and with any customary conditions contained in the any agreement
       entered into by the Company pursuant to this clause (xi);

          (xii)  prior to any public offering of Registrable Securities,
     cooperate with the selling Holders and their counsel in connection with the
     registration and qualification of the Registrable Securities under the
     securities or Blue Sky laws of such jurisdictions as the selling Holders
     may reasonably request and do any and all other acts or things necessary or
     advisable to enable the disposition in such jurisdictions of the
     Registrable Securities covered by the applicable Registration Statement;
     provided, however, that the Company shall not be required to register or
     qualify as a foreign corporation where it is not now so qualified or to
     take any action that would subject it to the service of process in suits or
     to taxation, other than as to matters and transactions relating to the
     Registration Statement, in any jurisdiction where it is not now so subject;

          (viii)  in connection with any sale of Registrable Securities that
     will result in such securities no longer being Registrable Securities,
     cooperate with the selling Holders to facilitate the timely preparation and
     delivery of certificates representing Registrable Securities to be sold and
     not bearing any restrictive legends; and to register such Registrable
     Securities in such denominations and such names as the selling Holders may
     request at least two Business Days prior to such sale of Registrable
     Securities;

                                       9
<PAGE>

          (xiv)  use its best efforts to cause the disposition of the
     Registrable Securities covered by the Registration Statement to be
     registered with or approved by such other governmental agencies or
     authorities as may be necessary to enable the seller or sellers thereof to
     consummate the disposition of such Registrable Securities, subject to the
     proviso contained in clause (xii) above;

          (xv)  provide a CUSIP number for all Registrable Securities not later
     than the effective date of a Registration Statement covering such
     Registrable Securities and provide the Transfer Agent or the Trustee, as
     the case may be, with printed certificates for the Registrable Securities
     which are in a form eligible for deposit with the Depository Trust Company;

          (xvi)  otherwise use its best efforts to comply with all applicable
     rules and regulations of the Commission, and make generally available to
     Holders with regard to any applicable Registration Statement, as soon as
     practicable, a consolidated earnings statement meeting the requirements of
     Rule 158 under the Act (which need not be audited) covering a twelve-month
     period beginning after the effective date of the Registration Statement (as
     such term is defined in paragraph (c) of Rule 158 under the Act);

          (xvii)  make appropriate officers of the Company available to the
     selling Holders for meetings with prospective purchasers of the Registrable
     Securities; and

          (xviii)  provide promptly to each Holder upon request each document
     filed with the Commission pursuant to the requirements of Section 13 or
     Section 15(d) of the Exchange Act.

     (b)  Restrictions on Holders.  Each Holder agrees by acquisition of a
          -----------------------
Registrable Security that, upon receipt of the notice referred to in Section 4
or Section 6(a)(i) or any notice from the Company of the existence of any fact
of the kind described in Section 6(a)(iii)(D) hereof (in each case, a

"Suspension Notice"), such Holder will forthwith discontinue disposition of
------------------
Transfer Restricted Securities pursuant to the Registration Statement until (i)
such Holder has received copies of the supplemented or amended Prospectus
contemplated by Section 6(a)(iv) hereof, or (ii) such Holder is advised in
writing by the Company that the use of the Prospectus may be resumed, and has
received copies of any additional or supplemental filings that are incorporated
by reference in the Prospectus (in each case, the "Recommencement Date").  Each
                                                   -------------------
Holder receiving a Suspension Notice hereby agrees that it will either (i)
destroy any Prospectuses, other than permanent file copies, then in such
Holder's possession which have been replaced by the Company with more recently
dated Prospectuses or (ii) deliver to the Company (at the Company's expense) all
copies, other than permanent file copies, then in such Holder's possession of
the Prospectus covering such Registrable Securities that was current at the time
of receipt of the Suspension Notice.  In the event the Company shall deliver a
Suspension Notice other than pursuant to Section 4, the time period regarding
the effectiveness of such Registration Statement set forth in Section 3 hereof,
shall be extended by a number of

                                       10
<PAGE>

days equal to the number of days in the period from and including the date of
delivery of the Suspension Notice to the date of delivery of the Recommencement
Date.

SECTION 7.  REGISTRATION EXPENSES

     (a)  All expenses incident to the Company's performance of or compliance
with this Agreement shall be borne by the Company, regardless of whether a
Registration Statement becomes effective, including without limitation: (i) all
registration and filing fees and expenses; (ii) all fees and expenses of
compliance with federal securities and state securities or Blue Sky laws; (iii)
all expenses of printing (including printing of Prospectuses), messenger and
delivery services and telephone; (iv) all fees and disbursements of counsel for
the Company and, in accordance with Section 7(b) below, the Holders of
Registrable Securities; (v) all fees and disbursements of independent certified
public accountants of the Company (including the expenses of any special audit
and comfort letters required by or incident to such performance); and (vi) fees
and expenses of the Transfer Agent, including the fees and expenses of its
counsel.

     The Company will, in any event, bear its internal expenses (including,
without limitation, all salaries and expenses of its officers and employees
performing legal or accounting duties), the expenses of any annual audit and the
fees and expenses of any Person, including special experts, retained by the
Company.

     (b)  In connection with any Registration Statement required by this
Agreement the Company will reimburse the Initial Purchasers and the Holders of
Registrable Securities being registered pursuant to the Shelf Registration
Statement for the reasonable fees and disbursements of not more than one
counsel, who shall be Latham & Watkins, unless another firm shall be chosen by
the Holders of a majority in principal amount of the Registrable Securities for
whose benefit such Registration Statement is being prepared.

SECTION 8.  INDEMNIFICATION AND CONTRIBUTION.

          (a) The Company agrees to indemnify and hold harmless (i) each Holder,
(ii) the directors, officers, employees and agents of each Holder and (iii) each
person who controls any Holder within the meaning of either the Act or the
Exchange Act (any person referred to in clause (i), (ii) or (iii) may
hereinafter be referred to as an "Indemnified Holder") against any and all
                                  ------------------
losses, claims, damages or liabilities, joint or several, to which they or any
of them may become subject under the Act, the Exchange Act or other Federal or
state statutory law or regulation, at common law or otherwise, insofar as such
losses, claims, damages or liabilities (or actions in respect thereof) arise out
of or are based upon any untrue statement or alleged untrue statement of a
material fact contained in any Registration Statement, preliminary prospectus or
Prospectus or any information provided by the Company to any Holder or
prospective purchaser of Preferred Stock or Preferred Stock Shares, as the case
may be, or in any amendment or supplement thereto, or arise out of or are based
upon the omission or alleged omission to state therein a material fact required
to be stated therein or necessary to make the statements therein, in the light
of the circumstances under which they were made, not misleading, and agree to
reimburse each such indemnified party, as incurred, for any legal or other
expenses reasonably

                                       11
<PAGE>

incurred by them in connection with investigating or defending any such loss,
claim, damage, liability or action; provided, however, that the Company will not
                                    --------  -------
be liable in any such case to the extent that any such loss, claim, damage or
liability arises out of or is based upon any such untrue statement or alleged
untrue statement or omission or alleged omission (i) made in any Registration
Statement, preliminary prospectus or Prospectus, or in any amendment or
supplement thereto, in reliance upon and in conformity with written information
furnished to the Company by any Holder specifically for inclusion therein or
(ii) made in any preliminary prospectus, if such untrue statement or omission or
alleged omission made in such preliminary prospectus is eliminated or remedied
in the Prospectus relating to it (as amended or supplemented, as applicable) and
a copy of such Prospectus shall not have been furnished to the person alleging
such loss, claim, damage or liability as required under applicable law. This
indemnity agreement will be in addition to any liability which the Company may
otherwise have.

          (b)  Each Holder of Registrable Securities severally agrees to
indemnify and hold harmless the Company, its directors, officers, employees and
agents and each person who controls the Company within the meaning of either the
Act or the Exchange Act, to the same extent as the foregoing indemnity from the
Company to each of the Indemnified Holders, but only with reference to written
information relating to such Indemnified Holder furnished to the Company by such
Indemnified Holder specifically for inclusion in any Registration Statement,
preliminary prospectus or Prospectus (or in any amendment or supplement
thereto).  This indemnity agreement will be in addition to any liability which
any Indemnified Holder may otherwise have.

          (c)  Promptly after receipt by an indemnified party under this Section
8 of notice of the commencement of any action, such indemnified party will, if a
claim in respect thereof is to be made against the indemnifying party under this
Section 8, notify the indemnifying party in writing of the commencement thereof;
but the failure so to notify the indemnifying party (i) will not relieve it from
liability under paragraph (a) or (b) above unless and to the extent it did not
otherwise learn of such action and such failure results in the forfeiture by the
indemnifying party of substantial rights and defenses and (ii) will not, in any
event, relieve the indemnifying party from any obligations to any indemnified
party other than the indemnification obligation provided in paragraph (a) or (b)
above.  The indemnifying party shall be entitled to appoint counsel of the
indemnifying party's choice at the indemnifying party's expense to represent the
indemnified party in any action for which indemnification is sought (in which
case the indemnifying party shall not thereafter be responsible for the fees and
expenses of any separate counsel retained by the indemnified party or parties
except as set forth below); provided, however, that such counsel shall be
satisfactory to the indemnified party.  Notwithstanding the indemnifying party's
election to appoint counsel to represent the indemnified party in an action, the
indemnified party shall have the right to employ separate counsel (including
local counsel), and the indemnifying party shall bear the reasonable fees, costs
and expenses of such separate counsel if (i) the use of counsel chosen by the
indemnifying party to represent the indemnified party would present such counsel
with a conflict of interest, (ii) the actual or potential defendants in, or
targets of, any such action include both the indemnified party and the
indemnifying party and the indemnified party shall have reasonably concluded
that there may be legal defenses available to it and/or other indemnified
parties which

                                       12
<PAGE>

are different from or additional to those available to the indemnifying party,
(iii) the indemnifying party shall not have employed counsel satisfactory to the
indemnified party to represent the indemnified party within a reasonable time
after notice of the institution of such action or (iv) the indemnifying party
shall authorize the indemnified party to employ separate counsel at the expense
of the indemnifying party. It is understood that the indemnifying party shall
not, in connection with any proceeding or related proceeding in the same
jurisdiction, be liable for the fees and expenses of more than one separate firm
(in addition to any local counsel) for all indemnified parties, and that all
such fees and expenses shall be reimbursed as they are incurred. Any such
separate firm for the Indemnified Holder and such control persons shall be
designated in writing by a majority of the Indemnified Holders and any such
separate firm of the Company, its directors, its officers and such control
persons of the Company shall be designated in writing by the Company. An
indemnifying party will not, without the prior written consent of the
indemnified parties, settle or compromise or consent to the entry of any
judgment with respect to any pending or threatened claim, action, suit or
proceeding in respect of which indemnification or contribution may be sought
hereunder (whether or not the indemnified parties are actual or potential
parties to such claim or action) unless such settlement, compromise or consent
includes an unconditional release of each indemnified party from all liability
arising out of such claim, action, suit or proceeding.

          (d)  In the event that the indemnity provided in paragraph (a) or (b)
of this Section 8 is unavailable to hold harmless an indemnified party for any
reason, the Company and the Holders agree to contribute to the aggregate losses,
claims, damages and liabilities (including legal or other expenses reasonably
incurred in connection with investigating or defending same) (collectively

"Losses") to which the Company and one or more of the Holders may be subject in
-------
such proportion as is appropriate to reflect the relative benefits received by
the Company, on the one hand, and by the Indemnified Holders, on the other hand,
from the sale of Registrable Securities; provided, however, that in no case
shall any Holder (except as may be provided in any agreement among the Holders
relating to the sale of its Registrable Securities) be responsible for any
amount in excess of the amount by which the total received by such Holder with
respect to its sale of Registrable Securities pursuant to a Registration
Statement exceeds the sum of (A) the amount paid to such Holder for such
Registrable Securities plus (B) the amount of any damages which such Holder has
otherwise been required to pay by reason of such untrue or alleged untrue
statement or omission or alleged omission. If the allocation provided by the
immediately preceding sentence is unavailable for any reason, the Company and
the Indemnified Holder shall contribute in such proportion as is appropriate to
reflect not only such relative benefits but also the relative fault of the
Company, on the one hand, and of the Indemnified Holder, on the other hand, in
connection with the statements or omissions which resulted in such Losses as
well as any other relevant equitable considerations.  Relative fault shall be
determined by reference to whether any alleged untrue statement or omission
relates to information provided by either the Company or the Holders and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission.  The Company and each Holder
agree that it would not be just and equitable if contribution were determined by
pro rata allocation or any other method of allocation which does not take
account of the equitable considerations referred to above.  Notwithstanding the
provisions of this paragraph (d), no person

                                       13
<PAGE>

guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of
the Act) shall be entitled to contribution from any person who was not guilty of
such fraudulent misrepresentation. For purposes of this Section 8, each person
who controls a Holder within the meaning of either the Act or the Exchange Act
and each director, officer, employee and agent of a Holder shall have the same
rights to contribution as such Holder, and each person who controls the Company
within the meaning of either the Act or the Exchange Act and each officer and
director of the Company shall have the same rights to contribution as the
Company, subject in each case to the applicable terms and conditions of this
paragraph (d). The remedies provided in this Section 8 are not exclusive and
shall not limit any rights or remedies which may otherwise be available to any
indemnified party at law or in equity.

SECTION 9.  RULE 144A

     The Company hereby agrees with each Holder, for so long as any Transfer
Restricted Securities remain outstanding and during any period in which the
Company is not subject to Section 13 or 15(d) of the Exchange Act, to make
available, upon request of any Holder of Transfer Restricted Securities, to any
Holder or beneficial owner of Transfer Restricted Securities in connection with
any sale thereof and any prospective purchaser of such Transfer Restricted
Securities designated by such Holder or beneficial owner, the information
required by Rule 144A(d)(4) under the Act in order to permit resales of such
Transfer Restricted Securities pursuant to Rule 144A.

SECTION 10.  MISCELLANEOUS

     (a)  Remedies.  The Company acknowledges and agrees that any failure by the
          --------
Company to comply with its obligations under Section 3 hereof may result in
material irreparable injury to the Initial Purchasers or the Holders for which
there is no adequate remedy at law, that it will not be possible to measure
damages for such injuries precisely and that, in the event of any such failure,
any Initial Purchaser or any Holder may obtain such relief as may be required to
specifically enforce the Company's obligations under Section 3 hereof.  The
Company further agrees to waive the defense in any action for specific
performance that a remedy at law would be adequate.

     (b)  No Inconsistent Agreements.  The Company shall not, on or after the
          --------------------------
date of this Agreement, enter into any agreement with respect to its securities
that is inconsistent with the rights granted to the Holders in this Agreement or
otherwise conflicts with the provisions hereof. The rights granted to the
Holders hereunder do not in any way conflict with and are not inconsistent with
the rights granted to the holders of the Company's securities under any
agreement in effect on the date hereof.

     (c)  Amendments and Waivers.  The provisions of this Agreement may not be
          ----------------------
amended, modified or supplemented, and waivers or consents to or departures from
the provisions hereof may not be given unless (i) in the case of Section 5
hereof and this Section 10 (c)(i), the Company has obtained the written consent
of the Holders of all outstanding Registrable Securities and (ii) in the case of
all other provisions hereof, the Company has

                                       14
<PAGE>

obtained the written consent of the Holders of a majority of the outstanding
principal amount of Registrable Securities (excluding Registrable Securities
held by the Company or its Affiliates). Notwithstanding the foregoing, a waiver
or consent to departure from the provisions hereof that relates exclusively to
the rights of Holders whose securities are being registered pursuant to the
Shelf Registration Statement and that does not affect, directly or indirectly,
the rights of other Holders whose securities are not being registered pursuant
to the Shelf Registration Statement may be given by the Holders of a majority of
the outstanding principal amount of Registrable Securities subject to such Shelf
Registration Statement.

     (d)  Third Party Beneficiary.  The Holders shall be third party
          -----------------------
beneficiaries to the agreements made hereunder between the Company, on the one
hand, and the Initial Purchasers, on the other hand, and shall have the right to
enforce such agreements directly to the extent they may deem such enforcement
necessary or advisable to protect their rights or the rights of Holders
hereunder.

     (e)   Notices.  All notices and other communications provided for or
           -------
permitted hereunder shall be made in writing by hand-delivery, first-class mail
(registered or certified, return receipt requested), telecopier or air courier
guaranteeing overnight delivery:

          (i)  if to a Holder, at the address set forth on the records of the
     Transfer Agent; and

          (ii)  if to the Company:

               Global Crossing Ltd.
               Wessex House
               45 Reid Street
               Hamilton HM12 Bermuda
               Telecopier No.:  (441) 296-8606
               Attention:  Secretary of the Company

               With a copy to:

               Simpson Thacher & Bartlett
               425 Lexington Avenue
               New York, NY  10017
               Telecopier No.:  (212) 455-2502
               Attention:  D. Rhett Brandon, Esq.

     All such notices and communications shall be deemed to have been duly
given:  at the time delivered by hand, if personally delivered; five Business
Days after being deposited in the mail, postage prepaid, if mailed; when receipt
acknowledged, if telecopied; and on the next Business Day, if timely delivered
to an air courier guaranteeing overnight delivery.

     (f)  Successors and Assigns.  This Agreement shall inure to the benefit of
          ----------------------
and be binding upon the successors and assigns of each of the parties hereto,
including, without limitation, and without the need for an express assignment,
subsequent Holders of Registrable

                                       15
<PAGE>

Securities; provided, that nothing herein shall be deemed to permit any
assignment, transfer or other disposition of Registrable Securities in violation
of the terms hereof or of the Purchase Agreement, Bye-laws or the Certificate of
Designations. If any transferee of any Holder shall acquire Registrable
Securities in any manner, whether by operation of law or otherwise, such
Registrable Securities shall be held subject to all of the terms of this
Agreement, and by taking and holding such Registrable Securities, such Person
shall be conclusively deemed to have agreed to be bound by and to perform all of
the terms and provisions of this Agreement, including the restrictions on resale
set forth in this Agreement and, if applicable, the Purchase Agreement, and such
Person shall be entitled to receive the benefits hereof.

     (g)  Counterparts.  This Agreement may be executed in any number of
          ------------
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

     (h)  Headings.  The headings in this Agreement are for convenience of
          --------
reference only and shall not limit or otherwise affect the meaning hereof.

     (i)  Governing Law.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
          -------------
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

     (j)  Severability.  In the event that any one or more of the provisions
          ------------
contained herein, or the application thereof in any circumstance, is held
invalid, illegal or unenforceable, the validity, legality and enforceability of
any such provision in every other respect and of the remaining provisions
contained herein shall not be affected or impaired thereby.

     (k)  Entire Agreement.  This Agreement is intended by the parties as a
          ----------------
final expression of their agreement and intended to be a complete and exclusive
statement of the agreement and understanding of the parties hereto in respect of
the subject matter contained herein.  There are no restrictions, promises,
warranties or undertakings, other than those set forth or referred to herein
with respect to the registration rights granted with respect to the Registrable
Securities.  This Agreement supersedes all prior agreements and understandings
between the parties with respect to such subject matter.

     (l)  Consent to Jurisdiction and Service.  To the fullest extent permitted
          ------------------------------------
by applicable law, the Company hereby irrevocably submits to the jurisdiction of
any Federal or State court located in the Borough of Manhattan in The City of
New York, New York in any suit, action or proceeding based on or arising out of
or relating to this Agreement or any Registrable Securities, and irrevocably
agrees that all claims in respect of such suit or proceeding may be determined
in any such court.  The Company irrevocably waives, to the fullest extent
permitted by law, any objection which it may have to the laying of the venue of
any such suit, action or proceeding brought in such a court and any claim that
any suit, action or proceeding brought in such a court has been brought in an
inconvenient forum. The Company agrees that final judgment in any such suit,
action or proceeding brought in such a court shall be conclusive and binding
upon the Company and may be enforced in the courts of Bermuda (or any other
courts to the jurisdiction

                                       16
<PAGE>

of which the Company is subject) by a suit upon such judgment, provided that
                                                               --------
service of process is effected upon the Company in the manner specified herein
or as otherwise permitted by law. The Company hereby irrevocably designates and
appoints CT Corporation System, 1633 Broadway - 23rd Floor, New York, New York
(the "Process Agent"), as the authorized agent of the Company upon whom process
      -------------
may be served in any such suit or proceeding, it being understood that the
designation and appointment of the Process Agent as such authorized agent shall
become effective immediately without any further action on the part of the
Company. The Company hereby represents to each Initial Purchaser that it has
notified the Process Agent of such designation and appointment and that the
Process Agent has accepted the same in writing. The Company hereby irrevocably
authorizes and directs the Process Agent to accept such service. The Company
further agrees that service of process upon the Process Agent and written notice
of said service to the Company mailed by prepaid registered first class mail or
delivered to the Process Agent at its principal office, shall be deemed in every
respect effective service of process upon the Company in any such suit or
proceeding. Nothing herein shall affect the right of any Initial Purchaser or
any person controlling any Initial Purchaser to serve process in any other
matter permitted by law. The Company further agrees to take any and all action,
including the execution and filing of any and all such documents and instruments
as may be necessary to continue such designation and appointment of the Process
Agent in full force and effect so long as the Company has any outstanding
obligations under this Agreement, the Registrable Securities, Bye-laws or the
Certificate of Designations. To the extent that the Company has or hereafter may
acquire any immunity from jurisdiction of any court or from any legal process
(whether through service of note, attachment prior to judgment, attachment in
aid of execution, executor or otherwise) with respect to itself or its property,
the Company hereby irrevocably waives such immunity in respect of its
obligations under this Agreement, to the extent permitted by law.


             [Registration Rights Agreement Signature Pages Follow]

                                       17
<PAGE>

     IN WITNESS WHEREOF, the parties have executed this Agreement as of the date
first written above.

                              Global Crossing Ltd.

                              By:
                                Name:
                                Title:

<PAGE>

The foregoing Agreement is hereby
confirmed and accepted as of the
date first above written.



Merrill Lynch, Pierce, Fenner & Smith Incorporated
Salomon Smith Barney Inc.
Goldman, Sachs & Co.
Chase Securities Inc.
Morgan Stanley Dean Witter & Co.
CIBC World Markets Corp.
Donaldson, Lufkin & Jenrette Securities Corporation
Credit Suisse First Boston Corporation


By:  Merrill Lynch, Pierce, Fenner & Smith Incorporated

By:_______________________________________
   Name:
   Title:


By:  Salomon Smith Barney Inc.

By:_______________________________________
   Name:
   Title:

For themselves and the other Initial Purchasers