Hot and humid conditons are expected in Osaka

The 11th World Athletics Championships begin in Osaka, Japan this weekend with a record 203 countries taking part.

Great Britain have sent a squad of 57 athletes with the target of bringing back just three medals.

UK performance director Dave Collins said: "Competition will be tough but we picked the strongest team possible to compete at the highest level."

The Worlds will see the first meeting in 2007 of 100m world record holder Asafa Powell and in-form Tyson Gay.

The heats for the men's 100m get under way on Saturday with the new track at the Nagai stadium reputedly capable of producing fast times.

Gay, who has a world-leading time of 9.84 seconds, is looking to go even lower in the hunt for his first major medal.

Powell's build-up to Osaka has been dogged by tendonitis in his knee and a groin injury, but both are unbeaten this season and everything is in place for an electric showdown.

"I am unbeaten, he is unbeaten and one of us is going to lose in Osaka," said Gay.

Marlon Devonish carries British hopes in the 100m along with Craig Pickering and Mark Lewis-Francis.

Gay wants to break the world 100m record at the Worlds

Devonish, who set a personal best of 10.06 seconds this summer, said: "If I've got Tyson Gay to the left of me and Asafa Powell to the right, I know I'm going to raise my game."

A streamlined Great Britain and Northern Ireland squad will be under pressure to perform well as Collins has set a target of 14 individual finalists.

Heptathletes Jessica Ennis and Kelly Sotherton aim to get the medal tally running in the first two days.

Sweden's imperious defending champion Carolina Kluft is favourite to take the multi-discipline crown again but Ennis is ranked third in the world while Sotherton always produces her best at major championships.

"It's going to be one of the most competitive fields at the Championships," said Sotherton, 30. "But I feel I couldn't be any more prepared."

Paula Radcliffe was the only Briton to win an individual medal at the Worlds in Helsinki in 2005.

But with the defending marathon champion not competing this time because of a back injury, Britain will be casting around for a solid gold individual medallist in Japan.

Commonwealth triple jump champion Phillips Idowu saw his podium chances improve following the withdrawal of Swedish Olympic champion Christian Olsson.

While Olsson misses out with an untimely hamstring injury, Idowu, 28, is on the comeback trail from a back problem as he seeks his first global medal.

Elsewhere, in the field, Chris Tomlinson (long jump) and Goldie Sayers (javelin) have also been in form this summer.

Britain's best medal chances on the track lie in the relays but there are several athletes who, on their day, are capable of world-class performances.

Mo Farah (5,000m), Michael Rimmer (800m) and Jo Pavey (10,000m and 5,000m) are amongst them.

I am going for victory and if I win maybe the record will come as well Jeremy Wariner

Another intriguing story developing on the track is Christine Ohuruogu's comeback from a one-year ban for missing out-of-competition drugs tests.

Just weeks after her ban expired, the 23-year-old Londoner has climbed to the top of the UK 400m rankings and could feature in Japan.

In the men's 400m, Texan Jeremy Wariner has his sights on breaking Michael Johnson's world record mark of 43.18 seconds.

"I am going for victory and if I win maybe the record will come as well," said Wariner, 23, who is also the defending world and Olympic champion.

Ethiopian Kenenisa Bekele goes for a third straight 10,000m title, just one short of distance legend Haile Gebrselassie's four successive crowns.

Bekele has decided not to contest the 5,000m so all eyes will be on Australian Craig Mottram, the reigning bronze medallist.

His compatriot Tirunesh Dibaba is going for both titles in Japan after becoming the first woman to capture the 5,000m and 10,000m titles in Helsinki.

Russian Yelena Isinbayeva is expected to once again dominate the pole vault competition.

China's world record holder Liu Xiang may go into the 110m hurdles as favourite but he will come under pressure close to home as he chases a first world gold.

Conditions in Osaka are expected to play a hand, however, throughout the nine days of competition.

It is expected to be hot, humid and even a little foggy in Osaka, where temperatures could climb as high as 40C.

Organisers have installed mist screens of water for marathon competitors to run through as, despite the 0700 start, temperatures could still reach 30C.