Paris  - Lance Armstrong's dream of winning an eighth Tour de France title burst on Sunday as he was left gasping in the wake of Alberto Contador's majestic ascent to the finish line in the Swiss ski resort of Verbier.

"He showed he's the best rider in the race," Armstrong told France 2 television after the 15th stage was run, and said he would now work to help his Astana teammate win the Tour.

The ease of Contador's victory and his flagrant superiority over his rivals on the climb makes it seem impossible, barring illness or injury, that anyone will overtake him in the final week of the race, which ends July 26 in Paris.

For Armstrong, who returned to the Tour after a three-and-a-half year "retirement," the 8km climb to the finish line represented a sobering return to reality.

"I definitely suffered," he said. "I was already a little at my limit at the bottom (of the climb). It was hard."

After Sunday's stage, Armstrong was in second place overall, 1 minute 37 seconds behind Contador.

Last week, Armstrong said he would not accept racing for a runner-up spot. On Sunday he declared, "I would take finishing in second place. I'm happy being second."

That was an astonishing admission from the man formerly known as The Boss on the Tour de France circuit. But from his performance in Sunday's stage, where he finished ninth and seemed to struggle on the climb, a second-place finish in the Tour will be difficult.

The Texas native, who came out of retirement to raise funds for his Livestrong cancer research foundation, will be spending the rest of this year's Tour in the unfamiliar role of water carrier.

"I'm hurting," he said Sunday with a grim smile.

Just about the only suspense remaining in the race is who will flank Contador on the podium in Paris.

That question will almost certainly be answered on the cruel slopes of Mont Ventoux, which will be climbed on the next-to-last stage of this year's Tour.

The 23-year-old Luxembourg rider Andy Schleck finished second on Sunday, 43 seconds behind Contador, and looked the best of the rest. Schleck now stands fifth, 2 minutes 26 seconds adrift, and less than a minute behind Armstrong.

But the ascent of Mont Ventoux represents a challenge of a different order from Sunday's climb in Switzerland, being nearly three times as long and even steeper.

The 2008 Tour winner Carlos Sastre is another possibility. He finished sixth on Sunday, 1 minute 6 seconds behind the winner, and is now 3 minutes 52 seconds off the lead.

The 34-year-old Sastre is usually at his best in the third week of the Tour and will surely be strong on July 25.

The joker in the field is named Bradley Wiggins. The 29-year-old Briton is better known as a speedster, having won three gold medals at the 2008 UCI World Track Championships. But he lost 8 kilos over the winter and has transformed himself into a formidable climber.

After Sunday's stage he lies in third place, only 9 seconds behind Armstrong. (dpa)