{blackbabes} Serena and Venus Williams to play Olympic doubles

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WIMBLEDON, England (AP) -- Serena and Venus Williams have been chosen to extend their unbeaten streak in Olympic doubles when they seek a third gold medal in the event next month.

Andy Roddick and John Isner were selected for men's doubles on the U.S. team announced on Tuesday.

As expected, the Olympic eligibility of the Williams sisters received final approval from the International Tennis Federation, and they'll play singles as well as doubles. They've never lost in Olympic doubles competition while taking the gold together in 2000 and 2008.

Venus Williams also won the gold in singles in 2000, and she's the only three-time gold medalist in U.S. tennis history. Next month she'll become the first American tennis player to compete in four Olympics.

Williams lost in the first round Monday at Wimbledon, which will also be the site of the Olympic tournament beginning on July 28. She expects to play both singles and doubles in the games even though she has been slowed in recent months by an autoimmune disease that causes fatigue.

As expected, the U.S. team includes first-time Olympians Ryan Harrison, Donald Young, Isner, Christina McHale and Varvara Lepchenko, born in Uzbekistan but who became a U.S. citizen in September.

Twins Bob and Mike Bryan, who won the bronze in 2008, will again compete in doubles, as will the top-ranked women's doubles team of Liezel Huber and Lisa Raymond.

Two U.S. teams in mixed doubles will be chosen once players are on site. That event returns to the Olympics after an 88-year absence.