From the Office of the US press secretary:
The President has asked Ambassador Ron Kirk, the U.S. Trade Representative, to represent the United States at the inauguration of the President of South Africa on May 9.  The President congratulates the people of on another successful election – the fourth in the post-apartheid period – and looks forward to a close working relationship with the incoming administration in South Africa.  Ambassador Kirk will be accompanied by senior members of the President’s administration.