Vittel, France - The 13th stage of the 2009 Tour de France got underway Friday in the north-eastern spa resort of Vittel.

The 200km course to the city of Colmar will take the 164 riders remaining in the race through the Vosges Mountains, with five climbs of varying difficulty, four of them coming in quick succession in the second half of the stage.

The most difficult of the ascents is the ride up to the Col du Platzerwasel, a climb of 8.7km at an average slope of 7.6 per cent that is rated Category 1 in difficulty.

It is one of four climbs that make up the second half of the stage and between which there is little time to rest for the riders. In addition, rain is forecast for the region, which could turn riding down the mountains into a dangerous undertaking.

Friday could be Italian Rinaldo Nocentini's last day in the race leader's yellow jersey. The 31-year-old AG2R rider leads Astana's Alberto Contador by 6 seconds, with seven-time Tour champion Lance Armstrong, also from Astana, 8 seconds back in third place.

If title contenders such as Australia's Cadel Evans or 2008 Tour winner Carlos Sastre of Spain try to use the stage to make up time on Contador and Armstrong, Astana will be forced to respond and Nocentini, who is not considered a top climber, could be left behind.

Contador and Armstrong received bad news Friday when one of Astana's strongest climbers, American Levi Leipheimer, pulled out of the race after suffering a broken wrist in a crash 3 kilometers from the finish of Thursday's 12th stage.

"Woke up to bad news. Levi is out with a broken wrist. Damn...," Armstrong reported on his Twitter feed.

Leipheimer was fourth overall, 39 seconds behind Nocentini, and was expected to play a vital support role in the decisive Alpine stages coming up next week.

"It's a hard blow to the team," Astana manager Johan Bruyneel said. "Its a good opportunity to attack us. But our strategy remains the same: wait for the others to attack and react according to the situation."

The Tour ends July 26 in Paris. (dpa)