EUGENE, Oregon (AFP) - World 100- and 200-meter champion Tyson Gay will not repeat his golden double at the Beijing Olympics after cramping and falling Saturday in a 200 heat at the US Olympic Track and Field Trials.

But fears of a major injury that would keep Gay from a Beijing 100-meter showdown next month against Jamaican stars Usain Bolt and Asafa Powell were eased when Mark Wetmore, Gay's agent, said there was no other apparent damage.

Gay, starting in lane seven, sped out of the blocks in the first 200 quarter-final heat and ran about 15 steps before falling to the track with what Wetmore termed a severe left hamstring cramp, stunning 20,000 at Hayward Field.

Wetmore said Gay had felt some tightness in the hamstring while warming up and that after Gay was carried off the track on a stretcher he had returned to his hotel room and was resting with his physiotherapist.

"I'm very disappointed," Gay said in a statement.

Gay ran the fastest 100 meters under any conditions last Sunday in a wind-aided 9.68 seconds to win the 100 final. But only the three top finishers in Sunday's 200 final will run in the event for the US team at the Olympics.

Bolt set the world record of 9.72 on May 31 at New York, beating Gay and breaking the old mark of 9.74 held by Powell.

A showdown among the three to decide who is the world's fastest man is expected to be among the signature moments of the Beijing Olympics.

An Olympic dream also died for 1996 Olympic 110 hurdles champion Allen Johnson, who at 37 was bidding for a fourth Olympics but pulled up after the fourth hurdle of his 110 hurdles qualifying heat.

Johnson said he injured a tendon in his left leg six weeks ago.

"I knew this was a possibility," Johnson said. "I hoped that it wouldn't happen, but it just didn't hold up. After the first hurdle, as I kept going, the pain just got progressively worse. This is really disappointing for me."

Two-time women's world champion Allyson Felix, thwarted in her bid for a 100-200 double by a fifth-place finish in the 100 final, led 200 finalists by winning her semi-final heat in 22.22, the fastest time by an American in 2008.

"I came out strong in the first 150 meters, so I could see where I was," Felix said. "I felt comfortable at that point and knew I had to maintain. I know there is more left in there so I'm really excited."

Muna Lee, the 100 winner, and fellow 100 qualifiers Torri Edwards and Lauryn Williams all advanced to the 200 finals, keeping alive Beijing double bids.

Finals in the 200 and hurdles will be among 10 finals Sunday on the last day of the meet, a lineup also including 1,500 and 5,000 world champion Bernard Lagat in the 1,500 as he tries to go for the same double at Beijing.

Reigning Olympic 200 champion Shawn Crawford won his semi-final heat in 20.21 for the best wind-legal run of those advancing to Sunday's final after Gay's shocking ouster in the earlier round.

Walter Dix, a 100 Olympian, Wallace Spearmon and Xavier Carter were also among the final eight, along with Rodney Martin, the other heat winner in 20.04 with a 2.2m/sec tailwind.

David Oliver, a May winner at Doha in 12.95, won his quarter-final heat in 13.07 seconds to lead 16 110 hurdles semi-finalists.

"I just came out and ran a decent race," Oliver said. "It's important to get through these two days before you think about Beijing."

Two-time Olympic runner-up and 2007 world runner-up Terrence Trammell was second to Oliver in 13.38 while David Payne, third at last year's worlds, was second in his heat in 13.22.

Women's world indoor 60m hurdles champion Lolo Jones had the fastest time in 100 hurdles quarter-finals, winning her heat in 12.59.

"I had a little goof up in the middle of the race but I recovered," Jones said. "I'm relaxed and can do my thing."

Reigning Olympic champion Joanna Hayes was second among 16 to advance, taking her heat in 12.65.

"It went OK," Hayes said. "I wasn't totally comfortable but it was fine and pretty clean."

Damu Cherry, who missed the 2004 trials while on a two-year doping ban, was second in her quarter-final heat in 12.86. The 30-year-old has this year's fastest time in the world this year, a 12.47 run in May.

Two-time world champion Michelle Perry, who resumed training six weeks ago after a hamstring injury, advanced with a fourth-place finish in 12.92.