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                                                                   EXHIBIT 10.79


**** Confidential material has been omitted and filed separately with the
Securities and Exchange Commission.


                                OPTION AGREEMENT

            OPTION AGREEMENT, dated as of February 12, 2001 (this "Agreement"),
by and among Williams Communications, LLC, a Delaware limited liability company
("Williams Communications"), Williams International Telecom Limited, a Cayman
Islands company ("WITL"), and Telecom Americas, Ltd., a company incorporated
under the laws of Bermuda (or any of its successors or permitted assigns,
"Purchaser").

            WHEREAS, Purchaser and The Williams Communications Group, Inc., a
Delaware corporation ("Williams") are parties to the Funding Agreement, dated as
of even date hereof (the "Funding Agreement"), by and among Williams, Purchaser,
ATL-Algar Telecom Leste S.A., a sociedade anonima organized under the laws of
the Federative Republic of Brazil (the "Company"), and the other parties listed
therein;

            WHEREAS, Williams Communications desires to grant to Purchaser an
option to purchase all, but not less than all, of its shares of and equity
interests in (the "Williams International Shares") Williams International ATL
Limited, a Cayman Islands company ("Williams International"), which owns all but
one of the quotas of and equity interests in Johi Representacoes Ltda. ("Johi")
and, subject to the completion of certain transfers discussed below, all but one
of the quotas of and equity interests in Algar Administradora de Sistemas
Opticos Ltda. ("Opticos"), each a limited liability company organized under the
laws of the Federative Republic of Brazil;

            WHEREAS, WITL desires to grant to Purchaser's designee an option to
purchase the remaining quota of and equity interest in Johi and, subject to the
completion of certain transfers discussed below, the remaining quota of and
equity interest in Opticos owned by WITL (together with all of the Williams
International Shares, the "Option Shares"); and

            WHEREAS, it is a condition precedent to the obligations of Purchaser
under the Funding Agreement that the parties hereto execute and deliver this
Agreement.

            NOW, THEREFORE, in consideration of the premises and the mutual
agreements and covenants hereinafter set forth, the parties hereto hereby agree
as follows:

                                  DEFINITIONS

            SECTION 1.01. Certain Defined Terms. As used in this Agreement,
terms defined in the Funding Agreement shall have the same meaning as defined
therein, and, in addition, the underlined terms defined in quotations herein
shall have the meanings ascribed to such terms herein.

            "Business Day" means any day that is not a Saturday, Sunday or other
day on which banks or stock exchanges are required or authorized by Law to be
closed in the City of New York or London.

            "LIBOR" means the rate per annum at which U.S. Dollar deposits were
offered for a one-month period shown on the Reuters Screen as at 11:00 a.m.
(London time) two Business Days in London prior to the date of determination of
such rate for delivery on the date


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of determination of such rate. For this purpose the "Reuters Screen" means the
display designated as the LIBOR 01 page on the Reuters system or such other page
as may replace the LIBOR 01 page on that system for the purpose of displaying
offered rates for U.S. Dollars deposits.

            "Repurchase Exercise Date" means the later of March 31, 2002 and the
anniversary of the date that Purchaser informed Williams Communications of its
intention not to acquire the Option Shares pursuant to Section 3.05(a) or
3.05(b)(i) or (b)(iii) hereof.

            "Repurchase Interest" means 50% of the rights and obligations of
Purchaser under the Funding Agreement and 50% of any common shares of the
Company issued to Purchaser or its designated Subsidiary pursuant thereto, which
shall be free and clear of any Encumbrances (except in favor of Ericsson and the
Lenders under the Secured Loan Agreement).

            "Repurchase Price", as of the date of any repurchase pursuant to
Section 2.04 or Section 2.06, means (a)(i) U.S.$150 million less (ii) 50% of any
amounts repaid to Purchaser pursuant to Section 2(d) of the Funding Agreement,
plus (b) interest on such amount payable in arrears at the rate of LIBOR plus 5%
per annum accruing from the date the Contribution was made to the Repurchase
Closing Date (as defined in Section 2.04 hereof).

                                   ARTICLE II
                                GRANT OF OPTION

            SECTION 2.01. Grant of Option. Williams Communications and WITL
hereby grant to Purchaser an irrevocable option to purchase the Option Shares in
accordance with the terms and conditions set forth herein (the "Option").

            SECTION 2.02. Exercise of Option. Purchaser may exercise the Option
by delivering a written notice (the "Exercise Notice") to Williams
Communications on or before March 31, 2001 (the "Expiration Date").

            SECTION 2.03. Termination of Option. If Purchaser has not delivered
the Exercise Notice to Williams Communications on or before the Expiration Date,
the Option shall terminate.

            SECTION 2.04. Williams Communications' Repurchase Right. If the
Option or this Agreement terminates pursuant to Section 2.03 or 3.05(a) or (b)
hereof, Williams Communications (or its permitted assigns) shall have the right
at any time on or before the Repurchase Exercise Date to acquire the Repurchase
Interest for a price equal to the Repurchase Price. If Williams Communications
elects to exercise its right to acquire the Repurchase Interest, it shall notify
Purchaser in writing of its intention to do so and the date on which it will do
so (the "Repurchase Closing Date"), which shall be at least 30 days after the
date on which it gives notice but no later than March 31, 2002. Upon receipt of
such notice, Purchaser shall promptly send Williams Communications written
notice of the Repurchase Price and the account to which the Repurchase Price
shall be paid. On the Repurchase Closing Date, Williams Communications shall
have deposited in the account specified by Purchaser the Repurchase Price in
U.S. currency, in immediately payable funds, and the Purchaser shall deliver
such documents as shall be necessary to assign and transfer the Repurchase
Interest.


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                                  ARTICLE III
                       PURCHASE AND SALE OF OPTION SHARES

            SECTION 3.01. Purchase and Sale. If Purchaser exercises the Option,
at the Closing (as defined below) Williams Communications and WITL shall sell,
assign, transfer, convey and deliver to Purchaser, and Purchaser shall purchase,
acquire, accept and take assignment and delivery of, from Williams
Communications and WITL, all of the right, title and interest of Williams
Communications and WITL in and to the Option Shares free and clear of any and
all Encumbrances. The aggregate purchase price in consideration of the Option
Shares shall be **** (the "Purchase Price") plus interest calculated pursuant
to Section 3.05(a)(ii) hereof, if applicable.

            SECTION 3.02. Closing Date. Except as hereinafter provided, the
closing of the purchase and sale of the Option Shares hereunder (the "Closing")
shall take place at the offices of Cleary, Gottlieb, Steen & Hamilton in New
York, New York, on the fifth Business Day following the date on which all of the
conditions contained in Section 3.03 have been satisfied or waived, as notified
by Purchaser or Williams Communications, as the case may be, or at such other
place and at such other time and date as may be mutually agreed upon by
Purchaser and Williams Communications. The date of the Closing is referred to in
this Agreement as the "Closing Date."

            SECTION 3.03. Conditions Precedent.

            (a) The obligation of Purchaser to consummate this Agreement and the
transactions contemplated hereby on the Closing Date shall be subject to the
satisfaction or waiver by Purchaser on such date of the following conditions:

                (i) Each of the representations and warranties made by Williams
     Communications and WITL hereunder shall be true and correct in all material
     respects as of the Closing Date with the same force and effect as though
     the same had been made as of the Closing Date.

                (ii) No Permit or waiver of, declaration or filing with or
     notification to any Person or Governmental Authority, including ANATEL, is
     required on the part of either party in connection with the transactions
     contemplated hereby other than such as have been given or made.

                (iii) Each of Williams Communications and WITL shall have
     performed and complied with in all material respects the covenants and
     provisions of this Agreement required to be performed or complied with by
     it between the date hereof and the Closing Date.

                (iv) No preliminary or permanent injunction or other
     Governmental Order of any court or tribunal or Governmental Authority of
     competent jurisdiction restraining, prohibiting or making illegal the
     consummation of the transactions contemplated hereby shall be in effect,
     threatened or pending.

     Redacted portions have been marked with asterisks (****). Confidential
     treatment has been requested for the redacted portions. The confidential
     redacted portions have been filed separately with the Securities and
     Exchange Commission.


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            (b) The obligation of Williams Communications and WITL to consummate
this Agreement and the transactions contemplated hereby on the Closing Date
shall be subject solely to the satisfaction or waiver by Williams Communications
and WITL on such date of the following conditions:

                (i) Each of the representations and warranties made by Purchaser
     hereunder shall be true and correct in all material respects as of the
     Closing Date with the same force and effect as though the same had been
     made as of the Closing Date.

                (ii) No Permit or waiver of, declaration or filing with or
     notification to any Person or Governmental Authority, including ANATEL, is
     required on the part of either party in connection with the transactions
     contemplated hereby, other than such as have been given or made.

                (iii) Purchaser shall have performed and complied with in all
     material respects the covenants and provisions of this Agreement required
     to be performed or complied with by it between the date hereof and the
     Closing Date.

                (iv) No preliminary or permanent injunction or other
     Governmental Order of any court or tribunal or Governmental Authority of
     competent jurisdiction restraining, prohibiting or making illegal the
     consummation of the transactions contemplated hereby shall be in effect,
     threatened or pending.

                (v) Williams Communications shall have received the irrevocable
     written release of Ericsson of the obligations of The Williams Companies,
     Inc., a Delaware corporation (the "Sponsor"), howsoever arising, under the
     Amended and Restated Sponsor's Undertaking, dated as of September 15, 1999
     (the "Sponsor's Undertaking"), issued by the Sponsor in favor of the Agents
     and Lenders (as defined under the Secured Loan Agreement).

                (vi) Williams Communications shall have received the irrevocable
     written release of its future obligations, howsoever arising, under the
     Guaranty Agreement, dated as of November 9, 2000 (the "Unibanco Guaranty"),
     by Williams Communications in favor of Unibanco for the banks and other
     financial institutions from time to time party to the Contrato de Abertura
     de Credito Mediante Repasse, dated as of November 9, 2000, by and among the
     Company, Unibanco and such banks and financial institutions.

                (vii) Williams Communications shall have received the
     irrevocable written release of its future obligations, howsoever arising,
     under the Guaranty Agreement, dated as of November 9, 2000 (the "BNDES
     Guaranty"), by Williams Communications in favor of BNDES.

            SECTION 3.04. Closing Deliveries. At the Closing, each of the
parties hereto shall deliver, or shall cause to be delivered, to the other party
the following:

                (a) Williams Communications and WITL shall (and shall cause
     Williams International to) execute and deliver the amendments to the
     Articles of


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Association of each of Johi and Opticos in form and substance acceptable to
Purchaser, transferring the quotas and equity interests in Johi and Opticos held
by WITL to an entity previously designated by Purchaser not less than 3 Business
Days prior to the Closing.

                (b) Williams Communications shall deliver to Purchaser the share
     register of Williams International duly amended by Williams International's
     registrar to show the transfer of the Williams International Shares to
     Purchaser, minute books and corporate seals of Williams International, and
     an amendment to the charter documents of Williams International effecting
     the change of name of Williams International to a name that does not
     contain the term "Williams", it being understood that Williams
     Communications shall effect the change of name to a name designated by
     Purchaser if Williams Communications receives Purchaser's selection not
     less than 3 Business Days' prior to the Closing.

                (c) Williams Communications shall deliver to Purchaser (i) the
     originals of the certificates of registration or a summary electronically
     issued by the Central Bank of Brazil evidencing all investments held by
     Williams International and WITL in the Capital Stock of the Company,
     Opticos and Johi, or (ii) documents that have been submitted to the Central
     Bank of Brazil that support the registration that will be issued by the
     Central Bank of Brazil.

                (d) Purchaser shall pay the Purchase Price to Williams
     Communications by transfer of immediately available funds to an account
     designated by Williams Communications, for itself and for the account of
     WITL, at least 3 Business Days prior to the Closing.

                (e) Each of the parties hereto shall receive any other
     certificates, legal opinions and documents required to be delivered by the
     parties hereunder.

            SECTION 3.05. Termination.

            (a) This Agreement may be terminated by the written agreement of
Purchaser and Williams Communications.

            (b) This Agreement shall terminate if the Purchaser has exercised
the Option and the Closing has not occurred within 60 days following the
Expiration Date; provided, however, that (i) upon mutual agreement, such 60-day
period may be extended for up to an additional 60 days in order to permit the
parties to fulfill the conditions precedent to Closing; (ii) if Williams
Communications or WITL has failed to satisfy its obligations under Section 4.03
hereof, at the option of Purchaser, such period shall be extended until the
earlier of the satisfaction of such requirement or the date that Purchaser
informs Williams Communications in writing of its intention not to purchase the
Option Shares; or (iii) if any Permit from (x) any Person, which is required
hereunder due to Williams Communications' or any of its Affiliates'
relationships (whether contractual or otherwise) with such Person (including,
but not limited to, the releases described in Sections 3.03(b)(v), (vi) and
(vii) hereof), or (y) ANATEL required in connection herewith (each, a "Critical
Permit") shall not have been obtained, such period shall be


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extended until the earlier of the receipt of such Permit or the date that
Purchaser informs Williams Communications in writing of its intention not to
purchase the Option Shares.

            (c) Upon any extension of the Closing pursuant to Section 3.05(b)
above, interest shall accrue on the Purchase Price from and after the date that
is 60 days after the Expiration Date at a rate of LIBOR plus 5% per annum until
such amount has been received by Williams Communications, and such interest, if
any, shall be payable concurrently with the Purchase Price; provided, however,
that if such extension is due to a failure by the parties hereto to receive a
Critical Permit, then interest shall not begin to accrue until such Permit or
Permits have been obtained.

            (d) Upon any termination of this Agreement pursuant to Section
3.05(a) or (b), no party hereto shall thereafter have any further liability or
obligation hereunder except for liabilities resulting from any breach of this
Agreement; provided, however, that this Section 3.05, Section 4.02(e), Section
5.02, Section 5.11 and Section 5.12 shall each remain in full force and effect
and the parties hereto shall remain liable hereunder to the extent indicated
herein.

                                   ARTICLE IV
                   REPRESENTATIONS, WARRANTIES AND COVENANTS

            SECTION 4.01. Representations, Warranties and Covenants of Williams
Communications and WITL. Each of Williams Communications and WITL, jointly and
severally, represents, warrants and covenants as follows, both as of the date
hereof and as of the Closing Date:

            (a) Williams International is a Cayman Islands company duly
organized, validly existing and in good standing under the laws of the Cayman
Islands and has all requisite corporate power and authority to own, lease and
operate its properties and to carry on its business as it is now being
conducted. True, correct and complete copies of Williams International's
organizational documents, each as amended to the date of this Agreement, have
been made available to Purchaser.

            (b) WITL and Williams International own beneficially and of record
all of the issued and outstanding Capital Stock and Convertible Securities of
Johi and, subject to the transfer of the ownership interest of SK Telecom Co.,
Ltd., a company organized under the laws of the Republic of Korea, in SKTI-US,
LLC, a Delaware limited liability company, to Williams International and/or
WITL, Opticos free and clear of any and all Encumbrances, and Williams
International does not, directly or indirectly, (A) own, of record or
beneficially, any Capital Stock or Convertible Securities of any other Person
(other than the shares of the Company owned by Williams International) or (B)
control any other Person. Such Capital Stock and Convertible Securities have
been duly authorized and validly issued, are fully paid and nonassessable, and
were not issued in violation of the pre-emptive rights of any Person or of any
agreement, Law or regulation by which the issuer of such Capital Stock and
Convertible Securities at the time of issuance was bound. None of such Capital
Stock and Convertible Securities is subject to any option, warrant, call, right
of conversion, exchange or purchase, or any similar right, whether oral or
written, and there are no agreements or understandings


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outstanding with respect to the voting or Transfer of any of such Capital Stock
and Convertible Securities.

            (c) The authorized capital stock of Williams International consists
of 50,000 shares of common stock, par value $1.00 per share, of which only the
Williams International Shares are issued and outstanding. The Williams
International Shares have been duly authorized and validly issued, are fully
paid and nonassessable, and were not issued in violation of the pre-emptive
rights of any Person or of any agreement, Law or regulation by which the issuer
of such shares at the time of issuance was bound. There are no outstanding
agreements which require Williams International to issue any Capital Stock or
Convertible Securities of Williams International. Williams Communications owns
the Williams International Shares free and clear of any Encumbrances. None of
the Williams International Shares is subject to any option, warrant, call, right
of conversion, exchange or purchase, or any similar right, whether oral or
written, and there are no agreements or understandings outstanding with respect
to the voting or Transfer of any of the Williams International Shares. The
delivery by Williams Communications to Purchaser at the Closing of the share
register of Williams International duly amended by Williams International's
registrar to show the transfer of the Williams International Shares to Purchaser
will vest Purchaser with good title to such shares, free and clear of any
Encumbrances.

            (d) Johi owns 43% of the preferred shares and 19% of the common
shares of the Company, and Williams International owns 22.5% of the preferred
shares of the Company (such shares, collectively, the "Company Shares"), free
and clear of any and all Encumbrances other than in favor of Ericsson and the
Lenders under the Secured Loan Agreement. Opticos owns the Promissory Note in
the amount of R$ 268,963,927.33 issued on December 29, 1999 by SBCI Brasil
Participacoes Ltda. free and clear of any and all Encumbrances . Johi owns all
of its rights under the AFACs free and clear of any and all Encumbrances other
than those in favor of Ericsson and the Lenders under the Secured Loan
Agreement. Except as set forth in any valid agreement among the shareholders of
the Company, none of the Company Shares is subject to any option, warrant, call,
right of conversion, exchange or purchase, or similar right, whether oral or
written, and there are no agreements or understandings outstanding with respect
to the voting or Transfer of any of the Company Shares.

            (e) Each of Williams International, Johi and Opticos was formed to
hold a direct or indirect interest in the Company and except for holding such
interests and the transactions related thereto, it has not engaged in any trade
or business or any other transaction, except certain other securities holdings
in other Persons by Williams International, which Williams International has
Transferred prior to the date hereof. Except as set forth in or referred to in
this Section 4.01, including certain rights in respect of SKTI-US, LLC and the
obligations of Williams International under the Credit Agreement, each of
Williams International, Johi and Opticos (A) does not have and has not had any
indebtedness, obligation or liability of any nature, whether accrued, absolute,
contingent or otherwise, whether due or becoming due, (B) is not and has not
been party to any agreement or arrangement with any other party, and (C) does
not have and has not had any real or personal property, tangible or intangible
right, or any other asset or right. Williams International, Johi and Opticos, as
the case may be, owns the assets set forth in this Section 4.01 free and clear
of any Encumbrances other than in favor of Ericsson and the Lenders under the
Secured Loan Agreement.


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            (f) The investments held, and to be held on the Closing Date, by
Williams International and WITL in the Capital Stock and Convertible Securities
of Johi and Opticos, and by Williams International in the Capital Stock of the
Company, (i) are duly registered with the Central Bank of Brazil as a direct
foreign investment in accordance with applicable Laws or (ii) have been
submitted to the Central Bank of Brazil for registration as a direct foreign
investment, and Williams International and WITL have provided the Central Bank
of Brazil with all information necessary for the issuance of such registration
and is not aware of any fact or circumstance that would prevent such
registration from being issued.

            (g) Except with the prior written consent of the Purchaser, Williams
Communications shall not, and shall not permit Williams International to, (A)
change or amend the organizational documents of Williams International or its
Subsidiaries, except for the change in name referred to in Section 3.04(b)
above, (B) issue or Transfer any Capital Stock or Convertible Securities of
Williams International or its Subsidiaries, (C) directly or indirectly, make or
solicit the Transfer of, or assume any Encumbrance with respect to, any of the
Option Shares, (D) directly or indirectly, redeem, purchase or otherwise acquire
any of the Option Shares, (E) make, or agree to make, any dividend or
distribution to any of Williams International's stockholders or any of their
Affiliates, (F) acquire or dispose of any fixed assets or other properties or
assets of Williams International or its Subsidiaries, (G) subject to any new
Encumbrance any of Williams International's or its Subsidiaries' assets or
properties, (H) other than as required under applicable Law, grant any increase
in salary to any employee or officer of Williams International or its
Subsidiaries, if any, (I) enter into any employment agreement with any officer
or employee of Williams International or its Subsidiaries, if any, (J) dispose
of or diminish the voluntary reserve of Williams International or its
Subsidiaries, or (K) enter into any contract, agreement, commitment or
arrangement with respect to any of the foregoing, except as permitted hereby.

            (h) To the knowledge of Williams Communications, after due and
diligent inquiry and assuming completion of the Contribution in full under the
Funding Agreement, Williams Communications hereby represents and warrants that
there exists no obligation of (i) the Sponsor under the Sponsor's Undertaking;
and/or (ii) Williams Communications under the Unibanco Guaranty and/or the BNDES
Guaranty.

            SECTION 4.02. Representations, Warranties and Covenants of each of
the Parties. Each of the parties hereto severally represents, warrants and
covenants as follows, both as of the date hereof and as of the Closing Date:

            (a) It is duly organized and validly existing under the Laws of the
jurisdiction of its organization, and it has the power and authority and the
legal right to execute and deliver this Agreement and perform its obligations
hereunder, and has taken all necessary action to authorize its execution,
delivery and performance of this Agreement.

            (b) This Agreement has been duly executed and delivered by it and
constitutes its legal, valid and binding obligation, enforceable in accordance
with its terms, subject to the effects of bankruptcy, insolvency, fraudulent
conveyance, reorganization, moratorium and other similar Laws relating to or
affecting creditor's rights generally, and general equitable principles (whether
considered in a proceeding in equity or at Law).


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            (c) The execution, delivery and performance of this Agreement by it
does not (i) violate, conflict with or result in the breach of any provision of
its organizational documents, (ii) conflict with or violate any Law or
Governmental Order applicable to it or any of its assets, properties or
businesses, or (iii) conflict with, result in any breach of, constitute a
default (or event which with the giving of notice or lapse of time, or both,
would become a default) under, require any consent under, or give to any other
Person any rights of termination, amendment, acceleration, suspension,
revocation or cancellation of rights of first refusal, rights of first offer,
change of control put, obligation to tender or other similar rights, or result
in the creation of any Encumbrance on any of its assets or properties pursuant
to, any note, bond, mortgage or indenture, contract, agreement, lease, sublease,
license, permit, franchise or other instrument or arrangement to which it is a
party or by which any of such assets or properties are bound or affected, which
would have a material adverse effect on its ability to consummate the
transactions contemplated by this Agreement.

            (d) To its knowledge, after due and diligent inquiry and except as
set forth in Article III above, no Permit or waiver of, declaration or filing
with or notification to any Person or Governmental Authority is required on the
part of such party in connection with the execution, delivery or performance of
this Agreement or the consummation of the transactions contemplated hereby.

            (e) It shall not hire or solicit for employment the employees of
the other party that are involved with the negotiations and the consummation of
the transactions contemplated hereby and by the Funding Agreement without the
prior written consent of such party.

            SECTION 4.03. Further Assurances. (a) Williams Communications shall,
and shall cause Williams International to, and WITL and Purchaser shall (i)
promptly take all such action as may be necessary, proper or advisable under
applicable Law for the consummation of the transactions contemplated hereby;
(ii) file and, if appropriate, use their or its best efforts to have declared
effective or approved all documents and notifications with, and to obtain any
consents of, all Governmental Authorities or other third parties that they or it
deem necessary or appropriate for the consummation of the transactions
contemplated hereby, including, without limitation, the consents, approvals and
waivers set forth in Article III; and (iii) give the other party information
requested by such other party pertaining to Williams International or Williams
Communications or WITL, in the case of requests by Purchaser, and Purchaser, in
the case of requests by Williams Communications or WITL, which is reasonably
necessary to enable such party or parties to take such actions and file in a
timely manner all documents and notifications required to be filed under
applicable Law.

            (b) If the Option is exercised, each of the parties shall execute
and deliver or cause to be executed and delivered all further documents and
instruments and use its reasonable best efforts to secure such Permits and take
all such further action as may be reasonably necessary in order (i) to
consummate the transactions contemplated hereby and (ii) to enable Purchaser to
exercise and enjoy all benefits and rights of Williams Communications and WITL
with respect to the Option Shares to be acquired upon such exercise of the
Option.

            SECTION 4.04. Survival and Indemnification. Each of the parties
hereto hereby agrees that the representations, warranties and covenants
contained in Sections 4.01 and


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<PAGE>   10


4.02 shall survive indefinitely. From and after the Closing Date, each party (an
"Indemnifying Party") agrees to indemnify fully, hold harmless, protect and
defend the other party and its Affiliates, and their respective directors,
officers, agents and employees, successors and assigns (the "Indemnified Party")
from and against: (i) any and all claims, demands, judgments, actions or causes
of action, liabilities, obligations, damages, losses, deficiencies, assessments,
costs, penalties, interest and expenses (including, without limitation, the
reasonable fees and expenses of counsel) (collectively, "Losses") incurred by
any of them arising out of, relating to or based upon any inaccuracy in, or
breach of, any of the representations or warranties of the Indemnifying Party
contained in Sections 4.01 or 4.02 hereof and (ii) any and all Losses incurred
by any of them arising out of, relating to or based upon any failure to perform,
or other breach of, any of the covenants or agreements of the Indemnifying Party
contained in Sections 4.01 or 4.02 hereof. The right of the Indemnified Party to
be indemnified hereunder shall not be limited or affected by any investigation
conducted or notice or knowledge obtained by it or on its behalf.

            SECTION 4.05. CADE Approval, Recission Rights. Each of Williams
Communications and WITL hereby acknowledges, covenants and agrees to use its
best efforts to cooperate in good faith with Purchaser to obtain any approval of
CADE required in connection with this Agreement or the Funding Agreement. If
such approval is denied or is granted subject to conditions that, in the
reasonable discretion of Purchaser, materially impair or detract from the value
of the Option Shares (each of the parties hereto hereby acknowledging that any
requirement imposed by CADE, other than as currently in effect under ANATEL
Resolution 101 or Decree No. 2056, of November 4, 1996 or any successor
regulations thereto, in connection with the granting of such approval that would
materially reduce the equity or voting interests in the Company that Purchaser
or any of its Affiliates would otherwise possess had such approval not been so
qualified would be a material impairment), then Williams Communications and
WITL, jointly and severally, hereby agree to repurchase the Option Shares at the
Purchase Price payable to the Purchaser in cash, in immediately available funds,
within 15 days of their receipt of a written notice from Purchaser stating that
CADE approval has been denied or that in Purchaser's reasonable discretion CADE
approval cannot be obtained without such an impairment or detraction.

                                   ARTICLE V
                                 MISCELLANEOUS

            SECTION 5.01. Expenses. Except as otherwise specified in this
Agreement, all costs and expenses, including, without limitation, fees and
disbursements of counsel, financial advisors and accountants, incurred in
connection with this Agreement and the transactions contemplated hereby shall be
borne by the party incurring such costs and expenses.

            SECTION 5.02. Notices. (a) All communications as they relate to this
Agreement shall be by facsimile or letter delivered by overnight or express mail
or courier. Each communication shall be made to the relevant party at the
facsimile number or address and marked for the attention of the Person(s) set
forth opposite such party's signature hereto unless specified otherwise in a
written notice by that party to the other parties for such purpose.

            (b) All communications delivered hereunder shall be in the English
language, and shall be deemed received (if by facsimile) when an acknowledgment
of receipt is received,


                                       10
<PAGE>   11



or (if by letter) when delivered, in each case in the manner required by this
Section 5.02; provided, that if a communication is received after business hours
it shall be deemed to be received and become effective on the next day which is
customarily considered a business day in the city to which such communication is
addressed. Once received, every communication shall be irrevocable except in
respect of any manifest error therein.

            SECTION 5.03. Headings. The descriptive headings contained in this
Agreement are for convenience of reference only and shall not affect in any way
the meaning or interpretation of this Agreement.

            SECTION 5.04. Severability. If any term or other provision of this
Agreement is invalid, illegal or incapable of being enforced by any Law,
governmental regulation or public policy, all other terms and provisions of this
Agreement shall nevertheless remain in full force and effect as long as the
economic or legal substance of the transactions contemplated hereby is not
affected in any manner materially adverse to any party. Upon such determination
that any term or other provision is invalid, illegal or incapable of being
enforced, the parties hereto shall negotiate in good faith to modify this
Agreement so as to effect the original intent of the parties as closely as
possible in an acceptable manner in order that the transactions contemplated
hereby are consummated as originally contemplated to the greatest extent
possible.

            SECTION 5.05. Entire Agreement. This Agreement constitutes the
entire agreement of the parties hereto with respect to the subject matter hereof
and supersedes all prior agreements and undertakings, both written and oral,
between the parties with respect to the subject matter hereof.

            SECTION 5.06. Assignment.

            (a) No party hereto may assign this Agreement or any right or
obligation hereunder without the express written consent of the other parties
hereto (which consent may be granted or withheld at their sole discretion);
provided, that (i) Purchaser may assign this Agreement or any of its rights or
obligations hereunder to any of its Subsidiaries; provided, that, at the time of
any assignment to such Subsidiary, America Movil owns at least 20% of the voting
Capital Stock of Purchaser calculated on a fully-diluted basis; and (ii)
Williams Communications may assign this Agreement or any of its rights or
obligations hereunder if (A) Purchaser (or any of its successors or permitted
assigns) (x) fails to exercise the Option under the Option Agreement on or prior
to March 31, 2001, or (y) fails to purchase such Option Shares after having
exercised such Option, and (B) any such failure is not attributable to (x) the
absence or unavailability of any Permit despite the reasonable best efforts of
America Movil (or its successors and permitted assigns , as the case may be) to
obtain or assist in obtaining such Permit or (y) a breach by Williams
Communications or WITL of its obligations under Section 4.03 of the Option
Agreement.

            (b) Purchaser may assign the Option in whole or in part to any
Person without the consent of Williams Communications or WITL, provided,
however, that Purchaser shall retain all its obligations and other rights
hereunder unless they have been assigned pursuant to Section 5.06(a).


                                       11
<PAGE>   12


            SECTION 5.07. No Third Party Beneficiaries. This Agreement shall be
binding upon and inure solely to the benefit of the parties hereto and their
permitted assigns and successors and nothing herein, express or implied, is
intended to or shall confer upon any other Person or entity, any legal or
equitable right, benefit or remedy of any nature whatsoever under or by reason
of this Agreement.

            SECTION 5.08. Amendment. This Agreement may not be amended or
modified, except by an instrument in writing signed by, or on behalf of, each of
the parties bound by, or subject to the provision to be amended or modified.

            SECTION 5.09. Counterparts. This Agreement may be executed by the
parties hereto in any number of separate counterparts, and all of said
counterparts taken together shall be deemed to constitute one and the same
instrument.

            SECTION 5.10. Specific Performance. The parties hereto agree that
irreparable damage would occur in the event any provision of this Agreement was
not performed in accordance with the terms hereof and that the parties hereto
shall be entitled to specific performance of the terms hereof, in addition to
any other remedy at Law or in equity.

            SECTION 5.11. Governing Law. This Agreement shall be governed by,
and construed in accordance with, the Laws of the State of New York applicable
to contracts executed in and to be performed in that State without regard to
conflicts of law.

            SECTION 5.12. Waiver of Jury Trial. Each of the parties hereto
irrevocably and unconditionally waives trial by jury in any legal action or
proceeding relating to this Agreement or the transactions contemplated hereby
and for any counterclaim therein.

            SECTION 5.13. Arbitration. Any controversy, claim or dispute arising
out of or relating to or in connection with this Agreement including, without
limitation, any dispute regarding its breach, termination, enforceability or
validity hereof shall be finally settled in the manner set forth in Section 16
of the Shareholders Agreement.

                                       12
<PAGE>   13



            IN WITNESS WHEREOF, the undersigned has caused this Agreement to be
duly executed and delivered by its duly authorized representative in New York,
New York, United States of America, as of the day and year first above written.

                                     TELECOM AMERICAS, LTD.


                                     By:  /s/ DANIEL HAJJ ABOUMRAD
                                        ----------------------------------------
                                     Name:  Daniel Hajj Aboumrad
                                     Title: Director


                                     By:  /s/ LOUIS TANGUAY
                                        ----------------------------------------
                                     Name:  Louis Tanguay
                                     Title: Director



                              Address for Notices:
                              Telecom Americas, Ltd.
                              Cedar House
                              41 Cedar Avenue
                              Hamilton
                              HM 12
                              Bermuda
                              Phone: ++441-295-2244
                              Fax: ++441-292-8666
                              Attention: Secretary



<PAGE>   14

            IN WITNESS WHEREOF, the undersigned has caused this Agreement to be
duly executed and delivered by its duly authorized representative in New York,
New York, United States of America, as of the day and year first above written.

                                     WILLIAMS COMMUNICATIONS, LLC


                                     By:  /s/ RODNEY JAY SAILOR
                                        ----------------------------------------
                                     Name:  Rodney Jay Sailor
                                     Title: Attorney-in-Fact


                              Address for Notices:
                              Williams Communications, LLC
                              One Williams Center
                              Tulsa, OK 74172
                              Fax: 918-573-6216
                              Phone: 918-573-2148
                              Attention: Mr. Rod Sailor


<PAGE>   15



            IN WITNESS WHEREOF, the undersigned has caused this Agreement to be
duly executed and delivered by its duly authorized representative in New York,
New York, United States of America, as of the day and year first above written.

                                     WILLIAMS INTERNATIONAL TELECOM
                                     LIMITED


                                     By:  /s/ RODNEY JAY SAILOR
                                        ----------------------------------------
                                     Name:  Rodney Jay Sailor
                                     Title: Attorney-in-Fact

                              Address for Notices:
                              Williams International Telecom Limited
                              One Williams Center
                              Tulsa, OK 74172
                              Fax: 918-573-6216
                              Phone: 918-573-2148
                              Attention: Mr. Rod Sailor