Trammell was second fastest in the world this year in both events

The American, second fastest in the world this year in both events, pulled up with a hamstring strain while finishing fifth in his heat of the 60m at the NIA in Birmingham.

US team manager Tim Weaver said later that Trammell had withdrawn from the 60m hurdles.

"He's out. The hamstring injury is serious enough that he has to pull out," said Weaver.

The news will improve Colin Jackson's chances of success in the 60m hurdles as the Welshman bids to end his international career with a gold.

Trammell was leading at the half-way point in his 60m heat but pulled up seven metres short and limped across the line, failing to qualify for the next round.

Trammell's injury was not the only blow for the American team on the first day of the three-day meet.

US national champion and gold medal hope Kevin Toth failed to qualify for the final of the shot put after finishing next-to-last in the preliminary round.

While three-time world outdoor champion John Godina led the qualifiers with a heave of 20.88m, Toth managed only 19.35, well off his world best of 21.70.