RIO DE JANEIRO - Usain Bolt has delivered a warning to his rivals ahead of next year's Rio Olympics by declaring he can beat anybody, irrespective of their form.

Jamaican Olympic gold medallist Usain Bolt greets youths at Mangueira slum Olympic center, ahead of the "Mano a Mano" challenge, a 100-meter race which will be held on this Sunday, in Rio de Janeiro April 16, 2015.  [Photo/Agencies]

In Rio de Janeiro for Sunday's Mano a Mano challenge, Bolt was asked about the threat posed by in-form US sprinter Justin Gatlin.

"They are all top-level athletes and I respect them all, but I don't think about their times because I know that when I' m on top form, I'm difficult to beat," Bolt told reporters on Friday.

The 28-year-old said he was in better shape now than at the same time last year. But he stopped short of saying he could break his own world record of 9.58 seconds at the Brazilian Jockey Club on Sunday.

"I'm feeling good, better than I did last year, but I'm not focused on times at the moment," he said. "I can only say that I will try to run (the 100m) in less than 10 seconds."

On Thursday Bolt revealed he was aiming for a landmark "triple-triple" by winning three more gold medals in Rio next year.

The Jamaican is two thirds of the way towards his goal, having triumphed in the 100m, 200m and 4x100m relay events at the Beijing 2008 and London 2012 Games.

He also revealed a desire to break the 200m world record.

A friend of Brazil captain Neymar, Bolt was questioned by journalists about Brazil's 7-1 World Cup semifinal defeat to Germany last July.

"I know Neymar is a fan of mine, and I am a fan of his too, and yes I did see the 7-1," he said.

"I didn't want to talk about this, but now you have asked me... it was a shock. Not only for me or for Brazil, but for the whole sporting world. Everyone thinks of Brazil as a powerhouse of football. But, as an athlete, I know that these kinds of things can happen to anybody."