Berlin - Trey Hardee of the United States regained the lead in the world championship decathlon after six events on Thursday while British star Paula Radcliffe said she won't run the marathon.

Radcliffe said in a statement issued by the British federation that she doesn't consider herself fully fit to go for gold on Sunday in the wake of foot surgery. Radcliffe is the world record holder and won the world title in 2005.

"I am devastated that I wasn't able to be ready in time to represent Britain here in Berlin, especially having got so close in such a short time frame," she said.

"However, after having the surgery to successfully put the years of injury behind me it is very important to me that I come back to racing often and winning at 100 per cent and continue strongly and successfully through to (the Olympics in) London 2012."

Hardee clocked 13.86 seconds in the 110 metres hurdles for a tally of 5,504 points, dethroning Ukraine's overnight leader Oleksiy Kasyanov, who had 14.55 seconds for
5,473 points.

Cuba's Yunior Diaz (5,415), Alexandr Pogorelov of Russia (5,325) and another Cuban, Yordani Garcia (5,312), are the other medal contenders.

Czech holder Roman Sebrle, who is the only man to score more than 9,000 points with a 2001 world record of 9,026, lies eighth 5,242 points and is not expected to medal this time after getting silver 2003 and 2005 before a 2007 gold.

Sebrle was furious on Wednesday night, saying he was not given enough time to rest ahead of the day's final event, the 400m, after a seemingly endless high jump round
(in which he cleared 2.11m).

"I think it's an international shame. This is just madness. I had a perfect high jump and I was among the last athletes to finish that event and they made me run the first heat at
400 just 20 minutes later," he fumed.

But competition director Paul Hardy told the German Press Agency dpa on Thursday that the break was 30 minutes according to the rules and that Sebrle declined an offer to run in a later 400m heat.

"We gave him the choice to run later," Hardy said.

The 400m races took place more than one hour later than originally scheduled. Hardy said that "the high jump went on way longer than we anticipated because of the large number of entries."

The decathlon was scheduled to continue throughout the day until the concluding 1,500m race in the evening.

However, the 200m final with Jamaican superstar Usain Bolt and a women's high jump duel between local Ariane Friedrich and Croatian holder Blanka Vlasic were expected to steal the headlines.

The other morning events were men's 800m heats and men's pole vault qualifying which took place without American holder Brad Walker, who is nursing a hip injury. (dpa)