Ethiopian world record holder Kenenisa Bekele tuned up for his Olympic defence by running the fourth-fastest 10,000 metres ever at the Prefontaine Classic, in Oregon, on Sunday.
Bekele, in a near-solo performance, clocked a crowd-pleasing 26:25.97 in his final 10,000 metres before Beijing's August Olympics.
"I did my best," Bekele said. "It's tough. I can't push more (faster) than this time."
Only Bekele and compatriot Haile Gebrselassie have run faster. Bekele was attempting to break his 2005 world record of 26:17.53 in his first outdoor US appearance.
Chinese 110 metres hurdles gold medallist and world record holder Liu Xiang, however, left questions about his Beijing preparations after a false-start disqualification.
He was disqualified for a false start after moving slightly at the beginning of his race. The false start was the second of the competition, meaning his automatic disqualification.
The top Chinese hope for an athletics gold medal at the August Games had run about 10 metres when the recall gun sounded.
"My speed is so fast I did not realise I had the false start," Liu said through a translator.
He pulled out of last week's New York meeting with a sore right hamstring, but said it was not causing him problems.
The Olympic champion now returns home to begin preparation for the Games and the biggest race of his life.
"Of course, I will run in the Olympics," he said. "The hamstring is not a problem."
American Anwar Moore won the race in a wind-assisted 13.09 seconds.
United States world pole vault champion Brad Walker showed his pre-Olympic Games fitness by soaring to a national record of 6.04 metres.
The mark was the best outdoor vault in seven years.
He missed twice at a world record 6.16 metres.
"Just because I did 6.04 today doesn't mean that the (US) trials will be easy," Walker said.
The American Olympic trials begin in Oregon on June 27 with only the top three finishers making the team for Beijing.
Olympic and world silver medallist Adam Nelson offered a preview of the Americans' strength in the shot put with the year's best put, 22.12 metres. World champion Reese Hoffa was second at 21.73.
Ethiopian Meseret Defar won the women's 5,000 metres in 14:38.73, and US double world champion Bernard Lagat took the infrequently run two-mile in 8:12.45.