Martigny, Switzerland  - The 16th stage of the 2009 Tour de France got underway Tuesday in the Swiss city of Martigny with Spanish rider Alberto Contador in firm control of the race.

The 159km course to the French city of Bourg-Saint-Maurice will take the 162 riders remaining in the race through three countries and up two long climbs.

The ascent to the Col du Grand-Saint-Bernard, located at the Swiss border with Italy, is 24.4km long and climbs at an average slope of 6.2 per cent to an altitude of more than 2,400 metres. It is rated Beyond Category in difficulty, the highest rating.

The climb up to the Col du Petit-Saint-Bernard, at the Italian border with France, covers a distance of 22.6km and is rated Category 1.

Because the peak of the second climb is located only 31km from the finish line, contenders for the Tour title may choose it for an attack on Contador.

The 26-year-old Spaniard leads his Astana teammate Lance Armstrong by 1 minute 37 seconds, with the surprising Briton Bradley Wiggins in third place, 1 minute 46 seconds behind.

But most analysts, as well as Contador himself, see the greatest danger coming from 23-year-old Andy Schleck of Luxembourg.

When the stage began, Schleck sat in fifth place, 2 minutes 26 seconds adrift, but he showed on Sunday's climb to the finish line in Verbier that he was the only rider capable of staying close to Contador's heels.

Schleck can also count on strong support from his Saxo Bank team, which includes his older brother, Frank.

"We are beginning the week about which I have thought, for which I have worked, since my first push on the pedals of the season," Andy Schleck said. "This is my week and I am ready."

Whether or not he can catch Contador, Schleck will have to ride aggressively to make it into the top three, because he will almost certainly lose more time to Armstrong and Wiggins during Thursday's individual time trial.

If he attacks Armstrong's second place, the entire Astana team will be forced to respond, which should create fireworks in the remaining three mountain stages.

Following Sunday's stage, several questions remained open regarding Armstrong's performance and intentions. Would he keep his word and help Contador win the title? And is he strong enough, after more than three years away from the sport, to keep up with the best on the long, gruelling Alpine climbs?(dpa)