Athletics: I'm not planning on losing to Justin Gatlin at World Champs, says Usain Bolt

Usain Bolt during the men's 100m race at the Diamond League in Brussels in September 2013. PHOTO: AFP

LONDON (GUARDIAN) - Usain Bolt insists he is in good enough shape to reclaim the title of the world's best sprinter from the controversial American Justin Gatlin.

The Jamaican, who has failed to fire so far this year, returns to the Olympic Stadium in London to compete in the 100m at the Anniversary Games on Friday night.

Bolt had a sharp retort when asked whether defeat to Gatlin at next month's world championships in Beijing would be bad for athletics, telling reporters: "I'm not planning to lose so I can't really answer that."

The Jamaican - who holds the records at both 100m and 200m - has largely watched on as Gatlin, who twice failed doping tests earlier in his career, has amassed a winning streak that stretches back to August 2013.

And while the American has regularly gone under 9.8sec for the 100m and posted four sub-20-second times for 200m this season, Bolt's best efforts for each distance are a rather more modest 10.12 and 20.13 respectively.

Injuries as well as poor conditions during his races have not helped, but the word from the Olympic and world champion's camp is that he is flying in training - and ready to show that he is in condition to go toe to toe with Gatlin in Beijing.

Said the 28-year-old Bolt: "I know Gatlin's been doing good this season, but I'm not worried. When the world championships comes anyone who knows anything about me knows I always show up. I'm just looking forward to going to Beijing. As long as I'm in great shape there will be no worries."

Gatlin's drug bans means he is not invited to race in Britain, and the pair have not raced individually against each other since 2013. Yet Bolt insists that he does not have a problem with Gatlin, despite his tainted past, because his failed drugs tests took place before he came on the international scene.

Instead he reserves his fire for Tyson Gay , who also served a ban after testing positive for testosterone two years' ago.

"The only person I have a problem with is Tyson," said Bolt. "I competed against him throughout the years and had so much respect for him. I looked at him as one of the greatest I have ever competed against.

"So when you hear that someone is cheating it really hurts as an athlete to know that the person you really look up to is banned for drugs. It really bothers me."

Bolt is close friends with Briton Mo Farah, who runs in the 3,000m immediately after Friday's 100m final, and the pair also share the agent Ricky Simms.

But while the Jamaican says he has not talked to Farah about the serious allegations made against his coach Alberto Salazar, he trusts him to make the right decision over whether to stand by the man who led him to 5,000m and 10,000m Olympic gold.

Said Bolt: "When you have confidence in your coach over the years and you know who he is as a person, of course you're going to want to support him as an athlete. If he believes in his coach I believe in him."

Bolt only decided to compete in London after the chancellor George Osborne announced in his budget that international athletes would be given tax-exempt status for the Anniversary Games.

That drew criticism in some quarters, but the Jamaican - whose addition to the bill a fortnight ago has led to a sharp increase in ticket sales and a forecast of a near-capacity 53,000 crowd - insisted he was worth his reputed £150,000 (S$318,510) fee.

"I always try to show my best performances and bring great crowds and it's always a great meet when I'm here," he said to laughter, "so I definitely think I'm worth it."

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