Exhibit 10.1

SUPPLEMENTAL AGREEMENT

This Supplemental Agreement (the “Agreement”) is entered into by AT&T Latin
America Corp. (“ATTL”), AT&T Argentina S.A. (“AT&T Argentina”) and Alejandro
Osvaldo Rossi (the “Executive”) as of April 1, 2002.

Recitals

  A.   The Executive serves as general manager of AT&T Argentina, a subsidiary
of ATTL, pursuant to an employment agreement dated June 30, 2000 (as amended
from time to time, the “Employment Agreement”).     B.   ATTL, AT&T Argentina
and the Executive have agreed upon certain protections for the Executive’s
compensation pursuant to the Employment Agreement, in consideration for
Executive’s undertakings herein and therein.

Now, therefore, the parties hereto agree as follows:

     1.     Subject to the other provisions of this Agreement, (i) AT&T
Argentina will make the compensation payments required under clauses (a), (b) or
(c) of Section 3 (and under clauses (a) and (b) of Section 5, if relevant) of
the Employment Agreement in U.S. dollars to the bank account or accounts of the
Executive as designated by the Executive from time to time by written notice,
and (ii) if AT&T Argentina is unable to pay to the Executive the full amount of
any such compensation payments, in U.S. dollars, due to exchange control,
convertibility or other similar legal restrictions existing or arising from time
to time in Argentina, ATTL will make payment promptly to the Executive of any
shortfall in such amount, to the bank account or account(s) of the Executive
designated by him by written notice. AT&T Argentina agrees to execute and
deliver to ATTL such notes, instruments or other documents as ATTL may request
from time to time in order to obtain reimbursement of any and all amounts paid
hereunder by ATTL, if any, to the maximum extent permitted by applicable law.
For the purpose of calculating the pertinent tax withholdings required to be
made in Argentina by AT&T Argentina, the Argentine peso equivalent amount of
each payment in US dollars will be determined, using the seller’s rate of
exchange quoted in the free market for the United States dollar by the Banco de
la Nación Argentina on the day on which such payment is made, or as of such
other date as may be permitted or required under applicable laws and
regulations.

     2.     Each of ATTL, AT&T Argentina and Executive acknowledges and agrees
that, except as provided specifically herein, (i) this Agreement does not create
any additional obligation of AT&T Argentina or ATTL to Executive, (ii) all
statutory contributions and withholdings required to be made under Argentine law
will be made by AT&T Argentina, and Executive shall be solely responsible for
any taxes (if any) imposed on Executive as a result of this Agreement, (iii) any
payment hereunder, if any, and under the Employment Agreement will be made only
in accordance with laws and regulations applicable to AT&T Argentina or ATTL, as
the case may be, (iv) the

 

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discharge by ATTL and AT&T Argentina of their respective obligations hereunder
and under the Employment Agreement are in each case subject to the performance
of Executive of his obligations hereunder and thereunder. Executive also agrees
that the provisions set forth in Sections 7 through 12, inclusive, in the
Employment Agreement will also have effect with respect to Brazil and to ATTL
and AT&T Brazil, as the context requires.

     3.     Executive agrees that, according to the request of ATTL, he will
spend time in the Sao Paulo and/or other offices of ATTL’s Brazilian subsidiary
(“AT&T Brazil”) during 2002, in order to manage AT&T Brazil’s operations during
any management transition undertaken in Brazil by ATTL or AT&T Brazil. Executive
acknowledges and agrees that this time spent will involve (i) initially, up to
two consecutive months beginning when notified by ATTL, (ii) after such initial
period, an expected 50% of each of the ensuing four months. Executive
acknowledges that the foregoing time schedule is based on ATTL’s expectation of
the management transition process in Brazil and is not definite. Executive
agrees to cooperate reasonably with ATTL and AT&T Brazil over the six months
following the initiation of a management transition in AT&T Brazil, as requested
by ATTL, provided that the time requested to be spent by Executive in Brazil is
not materially inconsistent with the periods specified above. Executive also
acknowledges that the time spent in Brazil is a special transitional project
assignment agreed by Executive and ATTL, in addition to Executive’s current
duties with respect to AT&T Argentina, but shall not constitute a formal
employment relationship between Executive and AT&T Brazil. It is understood that
AT&T Argentina will be the only employer of the Executive and that compensation
agreed in the Employment Agreement and herein shall constitute all compensation
due to Executive for services rendered by the Executive.

     4.     For the time Executive spends in Brazil, ATTL will cause AT&T Brazil
to pay or reimburse Executive for his reasonable out-of-pocket travel and living
expenses, in accordance with AT&T Brazil’s expense reimbursement policies for
its senior executives.

     5.     This Agreement shall terminate automatically upon any termination of
the Employment Agreement.

     6.     This Agreement shall be governed by and construed in accordance with
the laws of the State of New York, U.S.A. This Agreement may be executed in
counterparts, each of which shall be considered an original and all of which
together shall constitute one and the same instrument.

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In witness whereof, each of the parties has duly executed this Agreement as of
the date first written above.

  AT&T Latin America Corp.   /s/ Nelson Murphy/Edgardo Zayas

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Name: Nelson Murphy/Edgardo Zayas Title: CFO/Director, HR   AT&T Argentina S.A.
  /s/ Jorge Ortiz

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Name: Jorge Daniel Ortiz Title: Apoderado     Alejandro Osvaldo Rossi   /s/
Alejandro O. Rossi

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