World silver medallist LaShawn Merritt upset Olympic and World champion Jeremy Wariner for a convincing win in the US Olympic trials 400 metres on Thursday.

The 22-year-old Merritt, wearing the US colours of red, white and blue on a necklace, took the lead around 200 metres and surged to victory in 44.00 seconds.

Wariner finished second in 44.20 seconds with David Neville third in 44.61.

"Once I got into the home stretch I was smelling Beijing [Images] and victory," Merritt told reporters after making his first Olympic team.

The victory was Merritt's second over Wariner in three races this year. The former world junior champion surprised Wariner in the Golden League opener at Berlin in June with Wariner winning a semi-final race involving the two at the US trials on Monday.

But Merritt said the victory was not about out-running Wariner.

"My focus was not to beat anybody, my focus was to cross the finish line first," he said.

"He (Wariner) has been a champion for two years but it's a new year," Merritt said.

STILL FAVOURITE

Wariner told reporters he did not execute the race the way he wanted. "I just didn't run how I should have," he said. "I got to 200 meters and let (Merritt) get me in the end.

"I think I'm still the favourite (at the Olympics [Images])," he added. "I've been there before and I know what it takes to win."

Beijing favourite Sanya Richards won the women's 400 metres in 49.89 seconds.

Mary Wineberg took second in 50.85 seconds with Dee Dee Trotter placing third in 50.88 seconds.

Collegiate champion Brittney Reese won the long jump with the second-best mark of the year, 6.95 metres, and Anna Willard set a national record of 9:27.59 in the women's 3,000 metres steeplechase.

In qualifying, world 1,500 and 5,000 metres champion Bernard Lagat and national record holder Alan Webb advanced to the men's 1,500 metres semi-finals.