MONACO (AFP) - Usain Bolt may be struggling with a pelvic injury but the Jamaican should never be underestimated come next month's world championships, according to American arch-rival Justin Gatlin.

Bolt makes his comeback from an injury that saw him travel to Munich for treatment at the London Anniversary Games on July 24-25.

Gatlin, on a string of 26 unbeaten races dating back to August 2013, said Bolt should not be ruled out despite any talk of potential injury.

"We gave him good competition in the 2012 London Olympics and he prevailed. We'll have to step up a little more and give it some more competition," said Gatlin who won Olympic bronze behind Bolt and Yohan Blake.

"A lot of athletes are questioning if he'll be there in Beijing but everyone's really holding their breath to see how he'll go in the London race.

"One thing I can say about Usain is that he is a gamer, he's a showman, he'll rise to the occasion when it's time to do so. All that other stuff is not pressure for him.

"Usain woke up in the semi-finals in London in 2012 and went out there and did what he had to do and I predict (he'll be planning to do) the same thing for Beijing," said Gatlin.