Bourg-Saint-Maurice, France  - The 17th stage of the 2009 Tour de France, by consensus the most difficult of this year's race, got under way Wednesday in the Alpine resort of Bourg-Saint-Maurice.

The 169.5km course to the mountain village of Le Grand-Bornand includes five climbs, four of them rated Category 1 in difficulty, and should determine the top three finsihers of this year's Tour, which ends Sunday in Paris.

When the stage started, Spain's Alberto Contador held a lead of 1 minute 37 seconds over his Astana teammate Lance Armstrong, with the surprising triple 2008 UCI World Track gold medal winner Bradley Wiggins another 9 seconds back in third place.

The stage will show how strong Armstrong really is. The seven-time Tour champion returned to the sport after a retirement of nearly four years and is feeling the strain.

He said Tuesday that he would definitely ride in the Tour de France next year and would be in better condition.

French President Nicolas Sarkozy will be in attendance Wednesday, underscoring the importance of the stage, since the head of state is a fan of the Tour and knows something about the sport.(dpa)