WIMBLEDON, England -- 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 beginning late next month.Andy Roddick and John Isner were selected for men's doubles on the U.S. team announced 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, taking the gold together in 2000 and 2008.Venus Williams also won 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 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. roster includes first-time Olympians Ryan Harrison, Donald Young, Isner, Christina McHale and Varvara Lepchenko, an Uzbekistan native who became a U.S. citizen in September. Bob Bryan 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.Track and fieldWhy no tiebreaker? It's now taken three days and counting for USA Track and Field to sort out just who should fill the last American spot for the 100 meters at the London Games. Even high-tech cameras couldn't break a third-place tie between Allyson Felix and Jeneba Tarmoh in the final on Saturday. These are now the options: a runoff or a coin flip, with each raising questions from outside the track circle. Namely, why wasn't a plan already in place, such as in other sports? As it is, both are eligible to be selected to the 400-meter relay team. Also, there has been talk that perhaps Felix is waiting to see how she fares in the 200. Should she earn a spot in the 200 and Tarmoh doesn't, Felix might surrender the 100 spot to her training partner. Clay out of decathlon: Olympic decathlon champion Bryan Clay said he won't pursue a spot on the Olympic team in London after faltering at the U.S. track trials. Clay stumbled in the 110-meter hurdles then struggled in the discus in last weekend's multi-event competition, finishing in 12th place. Track's national governing body allows for the top three finishers in each event at the trials to earn a spot on the U.S. team, provided they have the "A" standard required to compete in the Olympics. Because only two U.S. decathletes had the standard -- trials winner Ashton Eaton and runner-up Trey Hardee -- only two spots on the team were filed. That led to some speculation that Clay might go for the standard at some point before the July 8 deadline.