Olympic champion Maurice Greene won the 100m at the Japan Grand Prix.
Greene will welcome his win after a series of injuries
The 29-year-old has been suffering with a series of injuries and had to miss last month's US indoor championships in February with a strained hamstring.
But he lead an American clean sweep of the podium places at the Nagai Stadium with a winning time of 10.04 seconds ahead of JJ Johnson and Mickey Grimes.
Meanwhile China's Liu Xiang upset Allen Johnson to win the men's 110m hurdles in 13.06secs.
Johnson, who finished with a time of 13.13, said: "To get a time of 13.06 this early in the season is impressive.
"I have been concerned about him ever since the world indoor
But he added: "I will get the gold in Athens. For me
to expect anything less is selling myself short."
Greene welcomed his win and, despite criticism of his own performance, said he was also confident of victory in Athens.
"I'm back," he said. "I'll make believers out of
them. If they don't believe in me now they soon will.
"I should have run faster. We've been here since Tuesday and maybe I left it
on the track in practice.
"But I wouldn't be running now if I didn't think I could win
gold in the Olympics."