BERLIN, Germany (CMC):

American sprinter Tyson Gay pulled out of a relay yesterday as a precautionary measure, a move aimed at ensuring his full fitness for next week's World Championships where he will show down with Jamaican sensation Usain Bolt.

The reigning double world sprint champion had planned to run in the 4x100 metres at Cottbus but said he was already focused on the August 15-23 showpiece scheduled to be staged in the historic German city.

"From here to the World Championships, I will be at 100 per cent of my capacities. I didn't want to take any risks," said Gay, who celebrates his 27th birthday today.He has been dogged by a nagging groin injury that has slowed his training but has assured he will be fit to race next week.

His clash with Bolt is expected to be the highlight of the World Championships, especially after his Beijing Olympics campaign was hampered by injury last year.

Gay has looked in ominous form, running the year's fastest times in both sprints, clocking 9.77 seconds in the 100 metres and 19.58 seconds in the 200 metres.

The 22-year-old Bolt, the double Olympic champion, holds the world record in both events after being timed at 9.69 in the 100 metres and 19.30 in the 200 metres in Beijing last August.