Terrence Trammell could cause the biggest upset of the Olympics if he breaks the tape ahead of Chinese champion Liu Xiang in the 110m hurdles on Aug 21.

The two-time Olympic silver medalist believes his time has come and the thought of disappointing up to a billion fans rooting for their home favorite will only inspire him further.

Trammell was hot on the heels of Liu at the Athens Games in 2004, when he came second, and their rivalry has intensified since then.

At the World Championships in Osaka last year, Trammell was leading the pack until Liu came from behind, pipping the United States athlete to the post by 0.04 seconds.

With such razor-thin margins at stake a reverse is easy to contemplate and the point was not lost on Trammell in an e-mail interview from his training camp in Atlanta. At this level, he said, winning or losing is as much a mind game as a physical battle.

"I think that the deciding factor will be the person that is able stay focused after already running three days in a row," he said.

"I think that my training and preparations are going really well. I'm healthy for a change and that's the biggest thing for me."

Both athletes are clearly at the top of their game right now. At 29, Trammell is the older athlete by 5 years, but age has not prevented him consistently improving his times. He clocked a personal best of 12.95 seconds in June last year, the eighth fastest of all time.

The 110m hurdles record holder, however, is Liu, who ran 12.88 in Lausanne, Switzerland in 2006. He also recorded the fastest time of last year, 12.92, alongside Cuba's Dayron Robles.

Trammell is well aware of Liu's ability.

"(He) is a very good athlete. He is always ready to compete on the big stage. Off the track Liu seems to be a carefree person who enjoys what he does. Even though he's under lots of pressure, he seems to handle it well."