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                                                                   EXHIBIT 10.30


                                                                  Execution Copy

                                GUARANTY BY FLAG


This GUARANTY, is made as of 29 December, 2000 by FLAG Telecom Holdings Limited,
a Bermuda company (the "Guarantor"), in favor of Level 3 (Bermuda) Ltd., a
corporation organized and existing under the laws of Bermuda, Level 3
Communications Limited, a corporation organized and existing under the laws of
Hong Kong and Level 3 Communications Limited, a corporation organized and
existing under the laws of Japan and their Affiliates (as defined in the
Development Agreement (as hereinafter defined)) made a party to the Agreements
(as hereinafter defined) (collectively referred to herein as "Level 3").

RECITALS

A.       Pursuant to a Submarine Cable System Development Agreement (as the same
         may from time to time be amended, modified or supplemented, the
         "Development Agreement"), dated as of the date of this Agreement,
         between FLAG Asia Limited, a company organized and existing under the
         laws of Bermuda (together with its successors and assigns "FLAG") and
         Level 3, have agreed to develop the FNAL System (as defined in the
         Development Agreement).

B.       In addition, FLAG and/or its Affiliates (as defined in the Development
         Agreement) and Level 3 have entered, or will or may enter, into the
         Transfer Agreement, the Fiber Pair Agreements and the Cable Station
         Agreements (as such terms are defined in the Development Agreement)
         (collectively, together with the Development Agreement, the
         "Agreements").

C.       Level 3 has required, as a condition precedent to entering into the
         Agreements to which it is a party, that the Guarantor execute and
         deliver this Guaranty. Level 3 would not enter into the Agreements with
         FLAG but for the execution and delivery of this Guaranty by the
         Guarantor.

D.       In furtherance of the business purposes of the Guarantor, the Guarantor
         desires to guaranty all of the obligations of FLAG under the Agreements
         as provided herein.

E.       The Guarantor is the owner either directly or indirectly of all of the
         capital stock of FLAG.

         NOW, THEREFORE, based upon the foregoing, and in order to induce Level
3 to enter into the Agreements to which it is a party, the Guarantor hereby
agrees as follows:

SECTION 1     DEFINITIONS. Capitalized terms not otherwise defined in this
         Guaranty shall have the meanings ascribed to them in the Agreements. As
         used in this Guaranty, the following terms have the following meanings
         unless the context otherwise requires:

1.1      "Guarantied Obligations" has the meaning ascribed to such term in
         Section 2.1.

1.2      "Guaranty" means this Guaranty, as it may be amended, supplemented or
         otherwise modified from time to time in writing signed by the Guarantor
         and Level 3.

SECTION 2     GUARANTY.

2.1      Guarantied Obligations. The Guarantor hereby unconditionally and
         irrevocably guarantees to Level 3 upon first written demand the full
         and punctual payment and performance by FLAG of all its obligations,
         liabilities and covenants now or in the future, under the Agreements,
         including, without limitation, the payment and performance of all
         damages and other remedies arising out of a failure of payment or
         performance (collectively, the "Guarantied Obligations"). The
         Guarantied Obligations shall conclusively be deemed to have been
         created in reliance upon this Guaranty.

2.2      Term of Guaranty.


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         2.2.1    This Guaranty shall remain in full force and effect until the
                  Guarantied Obligations are paid and performed in full.

         2.2.2    The Guarantor's performance or payment of a portion, but not
                  all, of the Guarantied Obligations shall in no way limit,
                  affect, modify or abridge the Guarantor's liability, as set
                  forth herein, for any portion of the Guarantied Obligations
                  that has not been completely performed or paid in full.

2.3      Guaranty Unconditional. The Guarantor agrees that the obligations of
         the Guarantor hereunder shall be unconditional and absolute and,
         without limiting the generality of the foregoing, shall not be
         released, discharged or otherwise affected by any of the following,
         whether with or without notice to or assent by the Guarantor:

         2.3.1    any extension, renewal, settlement, compromise, waiver or
                  release in respect of any obligation of FLAG under any of the
                  Agreements, by operation of law or otherwise;

         2.3.2    any modification or amendment of or supplement to any of the
                  Agreements;

         2.3.3    any release, impairment, non-perfection or invalidity of any
                  direct or indirect security for any obligation of FLAG under
                  any of the Agreements;

         2.3.4    any change in the corporate existence, structure or ownership
                  of FLAG, or any insolvency, bankruptcy, reorganization or
                  other similar proceeding affecting FLAG or its assets or any
                  resulting release or discharge of any obligation of FLAG
                  contained in any of the Agreements;

         2.3.5    the existence of any claim, set-off or other rights which the
                  Guarantor may have at any time against Level 3, FLAG, or any
                  other corporation or person, whether in connection herewith or
                  any unrelated transactions, provided that nothing herein shall
                  prevent the assertion of any such claim by separate suit;

         2.3.6    any invalidity or unenforceability relating to or against
                  FLAG, for any reason, of any of the Agreements, or any
                  provision of applicable law or regulation purporting to
                  prohibit the payment by FLAG of any other amount payable by
                  FLAG under any of the Agreements; or

         2.3.7    any other act or omission to act or delay of any kind by Level
                  3, FLAG, or any other corporation or person or any other
                  circumstance whatsoever which might, but for the provisions of
                  this paragraph, constitute a legal or equitable discharge of
                  or defense to the Guarantor's obligations hereunder.
                  Notwithstanding any provision of this Guaranty to the
                  contrary, the Guarantor shall be entitled to assert as a
                  defense to any claim for payment or performance of the
                  Guarantied Obligations, that:

                  2.3.7.1  such Guarantied Obligations are not currently due
                           under the terms of the Agreements; or

                  2.3.7.2  that such Guarantied Obligations have previously been
                           paid or performed in full.

2.4      Waivers of Notices and Defenses. The Guarantor hereby waives acceptance
         hereof, presentment, demand, protest and any notice not provided for
         herein, as well as any requirement that at any time any action be taken
         by any corporation or person against FLAG or any other corporation or
         person.

2.5      Stay. The Guarantor agrees that, notwithstanding anything to the
         contrary herein, if Level 3 is stayed upon the insolvency, bankruptcy,
         or reorganization of FLAG from exercising its rights to enforce or
         exercise any right or remedy with respect to the Guarantied
         Obligations, or is prevented from giving any notice or demand for
         payment or performance or taking any action to realize on any security
         or collateral or is prevented from collecting any of the Guarantied
         Obligations, in any such case, by such proceeding or action, the
         Guarantor shall pay or render to Level 3 upon demand therefor the
         amount or performance that would otherwise have been due had such
         rights and remedies been permitted to be exercised by Level 3.

2.6      No Enforcement of Subrogation. Upon making any payment or performance
         with respect to any Guarantied Obligation hereunder, the Guarantor
         shall be subrogated to the rights of Level 3 against FLAG


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         with respect to such payment or performance; provided that the
         Guarantor shall not enforce any payment or performance right by way of
         subrogation until all Guarantied Obligations have been paid and
         performed in full.

SECTION 3     REPRESENTATIONS AND WARRANTIES.

The Guarantor hereby represents and warrants to Level 3 that the following
statements are true and correct:

3.1      Binding Obligation. This Guaranty has been duly and validly executed
         and delivered by the Guarantor and constitutes the legal, valid and
         binding obligations of the Guarantor enforceable against the Guarantor
         in accordance with its terms, except as the enforceability thereof may
         be limited by bankruptcy, insolvency or other similar laws affecting
         the enforcement of creditors' rights generally and by equitable
         principles relating to the availability of equitable remedies.

3.2      Relationship to FLAG. As of the date hereof, the Guarantor is the
         owner, directly or through one or more wholly-owned subsidiaries, of
         all of the issued and outstanding capital stock of FLAG; the agreement
         of Level 3 to enter into the Agreements to which it is a party with
         FLAG is of substantial and material benefit to the Guarantor; and the
         Guarantor has reviewed and approved copies of the Agreements and all
         other related documents and is fully informed of the remedies Level 3
         may pursue upon the occurrence of a default under any of the
         Agreements. This Guaranty will remain in full force and effect if FLAG
         ceases to be a direct or indirect subsidiary of Guarantor.

3.3      Status. Guarantor is duly organized and existing under the laws of
         Bermuda.

SECTION 4     MISCELLANEOUS.

4.1      Delivery. Any notices, consent, approval, or other communication
         pursuant to this Agreement shall be in writing, in the English
         language, and shall be deemed to be duly given or served on a party if
         sent to the party at the address stipulated below and if sent by any of
         the following means only:

         4.1.1    Sent by hand: Such communication shall be deemed to have been
                  received on the Day of delivery provided receipt of delivery
                  is obtained.

         4.1.2    Sent by facsimile: Such communication shall be deemed to have
                  been received, under normal service conditions, twenty-four
                  (24) hours following the time of dispatch or on confirmation
                  by the receiving party, whichever is earlier.

         4.1.3    Sent by an internationally recognized courier service: Such
                  communication shall be deemed to have been received, under
                  normal service conditions, on the Day it was received or on
                  the third Day after it was dispatched, whichever is earlier.

         4.1.4    Sent by first class or air mail: Such communication shall be
                  deemed to have been received, under normal service conditions,
                  on the Day it was received or on the Day which is seven (7)
                  Days after the mailing thereof.

4.2      Addresses. For purposes of this Section, the names, addresses and fax
         numbers of the Parties are as detailed below. Any change to the name,
         address, and facsimile numbers may be made at any time by giving thirty
         (30) Days' prior written notice.

                  If to the Guarantor:           FLAG Telecom Holdings Limited
                                                 Suite 770
                                                 48 Par-la-Ville Road
                                                 Hamilton HM11
                                                 Bermuda

                  With a copy to:                FLAG Telecom Limited
                                                 9 South Street
                                                 London W1K 2XA
                                                 U.K.
                                                 Attn:  General Counsel


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                                                 Fax: +44 (20) 7317 0898

                  If to Level 3:                 Level 3 International, Inc.
                                                 66 Prescot Street
                                                 London E1 8HG
                                                 England
                                                 Attn: Legal Department
                                                 Fax: +44 (20) 7 864 0391

4.3      No Waivers. No failure or delay by Level 3 in exercising any right,
         power or privilege hereunder or under any of the Agreements shall
         operate as a waiver thereof nor shall any single or partial exercise
         thereof preclude any other or further exercise thereof or the exercise
         of any other right, power or privilege. The rights and remedies herein
         provided shall be cumulative and not exclusive of any rights or
         remedies provided by law.

4.4      Amendments and Waivers. This Guaranty constitutes the complete
         agreement of Level 3 and the Guarantor with respect to the subject
         matter hereof and supersedes all prior or contemporaneous negotiations,
         promises, covenants, agreements or representations. No amendment,
         modification, termination or waiver of any provision of this Guaranty,
         shall in any event be effective without the written consent of Level 3
         and Guarantor.

4.5      Successors and Assigns; Beneficiaries. This Guaranty is a continuing
         Guaranty and shall be binding upon the Guarantor and its successors and
         assigns, provided, however, that the Guarantor may not assign this
         Guaranty or transfer any of the rights or obligations of the Guarantor
         hereunder without the prior written consent of Level 3 and Level 3 may
         not assign this Guaranty as collateral without the prior written
         consent of the Guarantor. This Guaranty shall inure to the benefit of
         and may be enforced by Level 3 and its successors and permitted assigns
         under the Agreements. Nothing contained in this Guaranty shall be
         deemed to confer upon anyone other than the parties hereto and the
         other beneficiaries described in the preceding sentence any right to
         insist upon or to enforce the performance or observance of any of the
         obligations contained herein.

4.6      Applicable Law. This Guaranty shall be governed by and construed in
         accordance with the laws of the State of New York, United States
         without regard to its principles governing conflicts of law.

4.7      JURISDICTION. ANY ACTION OR PROCEEDING AGAINST THE GUARANTOR RELATING
         IN ANY WAY TO THIS GUARANTY MAY BE BROUGHT AND ENFORCED IN THE COURTS
         OF THE STATE AND CITY OF NEW YORK OR THE UNITED STATES FOR THE SOUTHERN
         DISTRICT OF NEW YORK, AND THE GUARANTOR IRREVOCABLY CONSENTS TO THE
         JURISDICTION OF EACH SUCH COURT IN RESPECT OF ANY SUCH ACTION OR
         PROCEEDING. THE GUARANTOR FURTHER IRREVOCABLY CONSENTS TO THE SERVICE
         OF PROCESS IN ANY SUCH ACTION OR PROCEEDING BY THE MAILING OF COPIES
         THEREOF BY REGISTERED OR CERTIFIED MAIL, POSTAGE PREPAID, RETURN
         RECEIPT REQUESTED, TO THE GUARANTOR AT ITS ADDRESS AS PROVIDED FOR
         NOTICES HEREUNDER. THE FOREGOING SHALL NOT LIMIT THE RIGHT OF LEVEL 3
         TO SERVE PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR TO BRING ANY
         ACTION OR PROCEEDING, OR TO OBTAIN EXECUTION OF ANY JUDGMENT, IN ANY
         OTHER JURISDICTION.

4.8      VENUE. THE GUARANTOR HEREBY IRREVOCABLY WAIVES ANY OBJECTION THAT IT
         MAY NOW OR HEREAFTER HAVE TO THE LAYING OF VENUE OF ANY ACTION OR
         PROCEEDING ARISING UNDER THIS GUARANTY IN ANY COURT LOCATED IN THE
         STATE AND CITY OF NEW YORK AND HEREBY FURTHER IRREVOCABLY WAIVES ANY
         CLAIM THAT ANY COURT LOCATED IN THE STATE OF NEW YORK IS NOT A
         CONVENIENT FORUM FOR ANY SUCH ACTION OR PROCEEDING.

4.9      WAIVER OF JURY TRIAL. THE GUARANTOR HEREBY IRREVOCABLY WAIVES ANY
         RIGHTS IT MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION
         BASED UPON, OR ARISING OUT OF, THIS GUARANTY OR ANY OF THE AGREEMENTS,
         OR ANY COURSE OF CONDUCT, COURSE OF DEALING, STATEMENTS OR ACTIONS OF
         LEVEL 3 OR THE GUARANTOR RELATING THERETO.


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4.10     Severability. If any provision in or obligation under this Guaranty
         shall be invalid, illegal or unenforceable in any jurisdiction, the
         validity, legality and enforceability of the remaining provisions or
         obligations, or of such provision or obligation in any other
         jurisdiction, shall not in any way be affected or impaired thereby.

4.11     Interpretation. Section headings in this Guaranty are included herein
         for convenience of reference only and shall not constitute a part of
         this Guaranty for any other purpose or be given any substantive effect.

4.12     Further Assurances. At any time or from time to time, upon the request
         of Level 3, the Guarantor shall execute and deliver such further
         documents and do such other acts and things as Level 3 may reasonably
         request in order to effect fully the purposes of this Guaranty. The
         Guarantor agrees to be liable for any reasonable expenses incurred by
         Level 3 and/or its successors and assigns with respect to any action or
         proceeding to enforce this Guaranty.

IN WITNESS WHEREOF, the Guarantor has executed this Guaranty as of the date
first above written.


FLAG TELECOM HOLDINGS LIMITED

-------------------------------------
Name:
Title:


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