EXHIBIT 10.62a




October 8, 1998



Mr. Ernest G. DeNigris
African Continental Telecommunications Ltd.
57/63 Line Wall Road
Gibraltar
Copy By Telecopier: 973/543-2559

Dear Mr. DeNigris:

Reference is made to (i) the Satellite Lease Agreement for the AMSC-1  Satellite
by and among AMSC Subsidiary  Corporation  ("American Mobile"),  American Mobile
Satellite Corporation and African Continental  Telecommunications Ltd. ("ACTEL")
dated December 2, 1997 (the "ACTEL Lease  Agreement")  and (ii) to the Satellite
Purchase  Agreement dated December 2, 1997 among TMI Communications and Company,
Limited  Partnership  and  AMSC  Subsidiary   Corporation  and  American  Mobile
Satellite  Corporation (the "TMI Purchase  Agreement").  Capitalized  terms used
herein without  definition  shall have the respective  meanings set forth in the
ACTEL Lease Agreement.

This letter  agreement  will confirm our  understanding  that,  contingent  upon
receipt by American Mobile of $2,500,000  from TMI,  American Mobile will refund
to ACTEL $2,500,000 of the $7,500,000 Initial Payment received from ACTEL. ACTEL
and American  Mobile agree that: (1) the ACTEL Lease Agreement will in all cases
be  interpreted  to account for this  repayment;  (2) in no event shall American
Mobile be liable to ACTEL for  repayment  of any further  portion of the Initial
Payment, regardless of cause and whether the ACTEL Lease Agreement is terminated
by American  Mobile or ACTEL;  and (3) no public  statements or filings by ACTEL
will assert any liability or cause for repayment.

In  addition,  American  Mobile and ACTEL agree to continue to negotiate in good
faith  towards the goal of achieving  the  following  by November 30, 1998:  (a)
ACTEL's receipt of a commitment by a strategic investor, reasonably satisfactory
to American Mobile, on terms sufficient to provide a reasonable basis to support
commencement  of the Initial  Lease Term prior to March 1, 1998;  (b)  agreement
between American Mobile and ACTEL on any changes to the ACTEL Lease Agreement to
obtain the commitment and commencement of the Initial Lease Term as described in
(a) above;  and (c) agreement  between American Mobile and TMI on any changes to
the TMI  Purchase  Agreement  which  would,  in  American  Mobile's  good  faith
judgment,  be required to implement the changes sought by ACTEL under (b) above.
American Mobile and ACTEL recognize that American Mobile's agreement to continue
negotiations  is subject to the receipt by American  Mobile of the  agreement of
TMI to act pursuant to or to amend the TMI  Purchase  Agreement in a manner that
would reasonably support such negotiations.








Mr. Ernest G. DeNigris
October 8, 1998
Page Two


All other  terms of the ACTEL  Lease  Agreement  shall  remain in full force and
effect and unamended  (except as set out above), no waivers of any provisions or
existing  defaults under the ACTEL Lease  Agreement shall be deemed to have been
made, and time shall remain of the essence.

Very truly yours,
/s/Gary M. Parsons
Gary M. Parsons


Agreed and Accepted this 9th day of October, 1998

AFRICAN CONTINENTAL TELECOMMUNICATIONS LTD.
/s/ Ernest G. DeNigris
- ---------------
By:      Ernest G. DeNigris
Its:     President