Usain Bolt, the world's fastest man, predicted yesterday he would retain his world 100 meters title in Daegu, South Korea, easily this month provided he gets a decent start.

"If I get a good start ... it won't be a problem for me," the lanky Jamaican said on the eve of his 25th birthday. "I think I will win with ease. When I get into my running stride I don't think anybody can match it, no matter my shape."

The 100 preliminaries take place on the first day of the championships on August 27 with the final on the following day. Bolt, whose 2010 season was curtailed because of injury, starts his 200 title defense on September 3.

Bolt said his primary aim was to defend his titles.

"There won't be any records here," added Bolt who smashed the world marks in the 100 and 200 at the 2008 Beijing Olympics and again at the world championships in Berlin the following year.

"Just to defend my titles, that is the main aim for me.

"A lot of people will be wanting a fast time so I think 9.7 (seconds) should be good," he said of the 100 meters.

Bolt's teammate Asafa Powell is the fastest man this year, clocking 9.78 seconds in Lausanne in June. His time is a tenth of a second quicker than anything the world record holder has managed this season.

"The injury kind of threw me off a lot," said Bolt. "I really couldn't push myself early season because you have to take it slowly. You can't really rush back into it."