EXHIBIT I
JOINT FILING AGREEMENT
In accordance with Rule 13d-1(k) under the Securities Exchange Act of
1934, as amended, the persons named below agree to the joint filing on behalf of
each of them of a statement on Schedule 13D dated December 20, 1999 with respect
to the Common Stock, par value $.01 per share, of American Mobile Satellite
Corporation, a Delaware corporation. This Joint Filing Agreement shall be
included as an Exhibit to such joint filing. In evidence thereof each of the
undersigned, being duly authorized, hereby executes this Agreement this 20th day
of December 1999.
SINGAPORE TELECOMMUNICATIONS LIMITED
By: /s/ Hoh Wing Chee
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Name: Hoh Wing Chee
Title: VP (International Network)
TEMASEK HOLDINGS (PRIVATE) LIMITED
By: /s/ Ong Xxx Xxxxx
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Name: Ong Xxx Xxxxx (Ms.)
Title: Vice President/
Company Secretary