OSLO (AFP) - Usain Bolt on Tuesday fired out a broadside at potential rivals at August's World Athletics Championships, saying that despite indifferent early season form his "eyes were on the prize".

The Jamaican has six Olympic gold medals to his name, and is reigning double world 200m champion and also world record holder in both the 100m and 200m.

But he sustained a blip in his exemplary career when he suffered a surprise defeat to American 2004 Olympic champion Justin Gatlin over 100m at the Rome leg of the 14-meet Diamond League circuit last week.

Bolt was quick to laugh off critics, saying that although a hamstring teak had set him back somewhat, he was not concerned about going to the worlds having suffered a loss, only his fourth in competition since 2008.

"This season started off pretty good, but I picked up a slight hamstring problem, which was a slight setback for me," he said ahead of Oslo's Bislett Games on Thursday.

"It's all about training to determine if I can get back to where I need to be to try to get back breaking records." Bolt added: "It's too early in the season to say what will be needed.

"Tyson (Gay)'s already there, Gatlin's running good but got beat by (Christophe) Lemaitre, and (Yohan) Blake's coming back from injury.

"We'll see what happens in the coming weeks."

Bolt, who dominated both the Beijing and London Olympics but lost his world 100m crown in Daegu in 2011 to compatriot Blake after a false start, said he was keen to notch up some more competitive racing after a prolonged period of training.

"I've trained very well. My legs felt great so I'm really happy," he said. "All I need right now is some races under my belt before the national trials."

The national Jamaican trials are where Bolt was infamously out-trumped in both the 100m and 200m by training partner Blake in 2012, just before the London Games.

That remains a fact important to remember, he stressed.

"At the end of 2008, I lost one race and won the Olympics that year. In 2010, which was my year off... Tyson beat me. Last year, Blake beat me at the national trials and I won the Olympics again, so it doesn't say much.

"All I'm concerned about is the championships.

"For me it's all about eyes on the prize, the 100m and 200m at the world championships at Moscow.

"I never try and think about one person. I'm definitely confident I can defend my titles.

"As I said, my eyes are on the prize."