Luxembourg's Kim Kirchen has pulled out of the world road race championships after citing a lack of form.

Kirchen was regarded as a medal contender in the men's road race to be held this Sunday but said he was in no condition to compete.

"I don't think I have sufficient form to get a good result, so I prefer not to compete," Kirchen, who wore the yellow jersey at this year's Tour de France, said Tuesday.

The team Columbia rider will be replaced by Claude Wolter in a team that will be led by the Schleck brothers, Andy and Frank. It is the first time ever that Luxembourg will have the luxury of using a nine-man team.

Walker in for Stuey
Meanwhile, Australian Stuart O'Grady will be replaced by compatriot William Walker for the men's road race on Sunday.

National Performance Director Shayne Bannan said O'Grady has been "feeling flat" since returning to Europe from Australia, where he headed for a short break after competing at the Olympic Games.

"He doesn't think he's in the form he needs to be to do the job for Australia this weekend and rather than let down the team he's decided not to compete," said Bannan.

Walker currently rides for the Dutch team Rabobank and lives and trains in Varese during the season and is very familiar with the course.

He was also on the Australian team for last year's World Championships in Stuttgart, where Italian Paolo Bettini took the second of his two world titles.

"I'm very, very happy about rejoining the team because it's a special honor to ride for Australia at the World Championships," said Walker, who has endured a difficult year due to illness and being hit a few times by cars while training.

"I've been riding reasonably well for the past couple of months though and when you ride for Australia you always ride above yourself and find something extra so I'm really motivated for Sunday. The fact that it's a few kilometers from my house makes it even better."

Walker joins Michael Rogers, Adam Hansen, Simon Gerrans, Allan Davis, Matthew Goss, Matt Lloyd, Trent Lowe and Robbie McEwen for the 260km road race on Sunday.

Bettini, the world champion in 2006 and 2007, is a big favorite here but will face a stiff challenge from several contenders, notably Spain's three-time world champion Oscar Freire.

Australia's best finisher at a world championships' road race was Belgium-based sprinter Robbie McEwen, who took the silver medal behind Italian Mario Cipollini at Zolder in 2002.