SYDNEY, Australia (AP) _ Second-seeded Alex O'Brien and Jared Palmer were upset in the first round of doubles at the Olympics, dropping the United States to 1-4 in men's tennis.

The only American still alive was Jeff Tarango, who won his opening singles match.

O'Brien and Palmer, making their Olympic debut, lost Friday (Thursday night EDT) to Mark Merklein and Mark Knowles of the Bahamas 6-2, 6-4.

Playing on Court 3 before 250 spectators, O'Brien and Palmer fell behind 4-0 and never had a break point. Merklein smacked four service winners in the final game to close out the match.

The doubles defeat was the most surprising setback yet for the U.S. men's tennis team. O'Brien and Palmer reached the semifinals of the Australian Open and the quarterfinals of Wimbledon this year.

In women's singles, fifth-seeded Spaniard Arantxa Sanchez-Vicario advanced to a likely quarterfinal showdown against second-seeded Venus Williams. Sanchez-Vicario, a four-time Olympic medalist, beat Colombian Fabiola Zuluaga 6-2, 6-0.

Williams took a 28-match winning streak into her third-round match later Friday (Thursday EDT). Her last loss came against Sanchez-Vicario at the French Open.