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.