Eugene, Oregon: Allyson Felix kept alive the possibility of a bid for a world championship double in the 200 and 400 metres as she clinched her first national 400m title at the US trials on Saturday.
Felix, challenged by runner-up Francena McCorory down the straight, ran strongly to the finish in 50.40 seconds and become the first woman to win US titles in the 100, 200 and 400m.
"I knew it was going to be racing home," said Felix, who has five US 200m titles and added the 100m last year.
"I wanted to be in position to use my speed."
McCorory clocked 50.49 to beat world indoor champion Debbie Dunn, who finished in 50.70. Felix, who will defend her 200m title at the August world championships in Daegu, South Korea, said she was undecided on whether she would attempt the double, but hoped to make the decision soon.
She also left open the possibility of doing as many as four events at the world championships and confirmed she would attempt the 4x100 and 4x400m relays.
Collegian Tony McQuay surprised former Olympic and world champion Jeremy Wariner for the men's 400m title. McQuay passed a tiring Wariner on the straight to clock a personal best 44.68 seconds.
"I never dreamed of doing this," he said of the win over Wariner, who eked out second place over Greg Nixon. Both were timed in 44.98.
But McQuay said he also had bigger ambitions.
"I want to break the world record," the 21-year-old said.
"I've got my mind set on that." Wariner had the disadvantage of a tight inside lane, but still had the lead off the final bend.
"The last 100 metres were not what I wanted it to be," he said. "I tightened up a little before he passed me."
But Wariner said it was not time to panic.
"By worlds, I will be perfectly fine," he said.
Top-ranked David Oliver claimed the 110m hurdles title in 13.04 seconds. Aries Merritt and Jason Richardson followed as two-time former Olympic silver medallist Terrence Trammell failed to make the team.
Only the top three finishers in each event qualify for the American squad in Daegu. The US team, already without injured 100m world silver medallist sprinter Tyson Gay, lost former world champion Brad Walker in the pole vault when he no-heighted. Walker had the best mark in the world this season at 5.84 metres.
In qualifying, former Olympic gold medallist Shawn Crawford caught a big wind to set the pace in 20.24 seconds in the 200m. Walter Dix, the new 100m US champion, was also comfortably through in 20.52.
Former Olympic and world sprint champion Justin Gatlin, who put a four-year doping ban behind him with a runner-up finish in Friday's 100m trial, sat out of the 200m trial.