BERLIN (AP):

At first sight, the World Championships are all about Usain Bolt, the Jamaican sprinter who seems to rake in Olympic gold medals and world records at will.

This time though, Tyson Gay is in good shape and the triple defending world champion has the year's best times to prove it.

That duel on the blue track of the Olympic Stadium also represents a bigger theme dominating the August 15-23 championships: will Jamaica be able to maintain its stunning sprint domination over the United States, or will Gay and Allyson Felix, another triple world champion, re-establish the traditional US domination?

The marquee battle gets under way immediately on Saturday morning with the opening heats in the men's 100 metres. The final is on Sunday night. The overall fight for supremacy won't be over until the next Saturday when the men's sprint relay finals finish.

Ready to go

After Bolt turned Beijing into a one-man show, Gay is healthy and ready after seeing his 2008 season ruined by a hamstring injury.

"Everyone knows last year, the big matchup - if that's what you want to call it - didn't happen. I'm really looking forward to it this year," said Gay, who won the 100 and 200 in Osaka, Japan, in 2007 and helped the US team capture the relay gold.

Bolt injured his foot following a car crash early this year, which has affected his work on the bend in the 200. Gay has had a groin ache recently but says it will not bother him at the championships.

After Bolt set three world records in as many events in Beijing, there were expectations that he would be unrivalled for years to come.

On this season's list of top times, however, he is second to Gay in both sprint distances.

Gay ran 9.77 in the 100 in Rome last month, compared to Bolt's 9.79 in Paris. In the 200, the American ran 19.58 in New York, just .01 faster than Bolt's time in Lausanne, Switzerland.

Favourable breeze

That doesn't necessarily make Gay faster, since Bolt ran both races in the rain and into a wind, while Gay had a favourable breeze and good conditions.

Berlin, though, will be the first time they face each other this year.

"I've always felt in my mind that I could challenge him," Gay said. "It's not like he's always been the world record-holder or he's always been the Olympic gold medallist.

"He's always been Usain Bolt to me. I've beaten him before, he's beaten me before."

The US team will be counting heavily on Gay to make sure it does better than last year, when its 23 Olympic medals included only seven golds. Two years ago in Osaka, they had 14 golds and 26 overall to easily top the medal standings.

The US women also failed to win a sprint gold at Beijing, where Jamaica took the individual titles but then dropped the baton in the relay for the only blemish in a near-perfect cham-pionships.

Felix was a huge disappointment then, but is hoping for a better showing this time.

She will be looking for a third world title in a row after losing to archrival Veronica Campbell-Brown in Beijing.

"Jamaicans are always running fast so those will be the main ones" to challenge, Felix said.

Like Bolt, women's pole vaulter Yelena Isinbayeva can challenge the world record every time she competes. The standout Russian set the current mark of 5.05 metres in Beijing, but has not come close to that this year.

Big jumps

She has even been beaten this year, when Anna Rogowska of Poland edged her in London last month. Isinbayeva though, has an uncanny knack for coming up with the big jumps when it counts.

On the track, Kenenisa Bekele is going for his fourth consecutive 10,000-metre title to follow his long-distance double in Beijing.