CHATEAUROUX-DEOLS, France, July 21 AAP - Mark Cavendish's withering turn of speed to win stage 18 of the Tour de France also sent a chilling warning to rival nations ahead of the Olympics.

The in-form Cavendish looms as the favourite to win the road race gold medal on July 28, now just a week away, after the British world champion unleashed one of the best sprints of his storied career to win on Friday in Brive-la-Gaillarde.

He now has 22 stage wins in the Tour, equalling the most by a sprinter.

Cavendish is also favourite for the 250km road race in London - a day after the opening ceremony and one of the feature events of the Olympics.

But there is no guarantee it will come down to a sprint.

Each nation is only allowed a maximum of five riders, which will make it much harder for teams to execute the tactics that are so essential in road cycling.

The nine laps of the hilly Box Hill circuit in Surrey midway through the race will add to the difficulty.

Cavendish has intentionally shed weight to be ready for the road race and has climbed reasonably well during the Tour.

"It wasn't easy today, it's not been an easy Tour with a lot of tired legs and Cav was there, on that climb at the end when others had bailed out," said Sean Yates, the director of Cavendish's Sky team.

"It's going to be complicated - only five riders per team, I'm not sure.

"He has a fantastic chance, he's climbing well, he's obviously sprinting well - he has as good a chance as any."

The positive for Cavendish is that he will have a strong team around him.

His teammates will include impending Tour de France champion Brad Wiggins, second-placed Chris Froome and stage winner David Millar.

"The name that jumps out (as a main rival) is (Slovakian) Peter Sagan, but Cav is faster than him," Yates said.

"They have to get rid of Cav. Cav has a team built around him.

"It's not impossible that he can be brought back to the bunch by the likes of Bradley and David Millar."

Australia's main medal option is sprinter Matt Goss, but they have also picked a team with a couple of options to cater for different tactical scenarios.

NZ Newswire