Andy Schleck led a daring attack to win the 18th stage of the Tour de France on Thursday, leaving Thomas Voeckler clinging to the yellow jersey and defending champion Alberto Contador out of contention.

Contador had a dismal final climb, and the Spaniard insists his chances are gone for a fourth title in cycling's showcase race.

"Victory is impossible now," he said. "I had a bad day. My legs didn't respond and I just hit a wall. It was a very difficult day right from the start."

Schleck began the day in fourth place and is now 15 seconds behind Voeckler. He attacked his top rivals on the second of three grueling climbs and held on all the way on the fabled Galibier pass to the highest-altitude finish in the race's 108-year history.

"I told the team yesterday that I had this in mind. I wasn't going to be fourth in Paris," Schleck said. "I said I'd risk it all. ... It's my character: I'm not afraid to lose."

"I felt super good today," the Luxembourg rider added. "Tomorrow is another day, and I hope to have the yellow jersey."

Interestingly Schleck did not repeat his criticism of the Tour's descents after today's stage in which Schleck was successful - contrary to what has been the case in the last two days.

Frank Schleck finished second today, trailing his brother by 2 minutes, 7 seconds. Cadel Evans of Australia was third over the 125-mile route from Pinerolo. Voeckler was fifth on Thursday, 2:21 behind. Frank Schleck was third overall, 1:08 back.

Contador was the day's biggest loser, trailing in 15th place -- 3:50 behind. Overall, he trails the French leader by 4:44 in seventh place.

"Please, let me breathe," an exhausted Voeckler said at the finish, mustering the strength to raise a fist in joy once he saw he'd kept the yellow jersey. "At 2,650 meters, the oxygen is thin."

"I limited the damage," he added. "I went all out."

Schleck, the Leopard Trek team leader, came in knowing that he would need to gain time on rivals ahead of Saturday's time trial -- a discipline that's not his specialty.

On Friday, the pack faces the last of three days in the Alps. It again features an uphill finish at the renowned and dreaded Alpe d'Huez.

Ahead of the stage, Contador tweeted in Spanish about "What leg pain!" awaits on three climbs so tough they defy cycling's rating climbs: the Col d'Agnel, the Col d'Izoard and the Col du Galibier.

The pack scaled more than 37 miles of total climbs, about one-third of which had a gradient of more than 9 percent. Tour director Christian Prudhomme called the 15-mile Col d'Agnel (9,000 feet) the hardest climb in this year's race.

Agnel, the day's first big climb, wasn't the site of the showdown. At one point there, Contador drifted back to the race doctor for a check, though it wasn't immediately clear why.

Instead, Andy Schleck took his chance on Col d'Izoard. After riding behind Leopard Trek teammate Stuart O'Grady, he sped from the main pack about midway up, with 13 breakaway riders ahead.

Contador moved up to the front of the pack but didn't chase. Neither did Voeckler or Evans, possibly a tactical error that could cost them victory in Paris on Sunday.

The stage showed how teamwork and strategy can be essential. Leopard Trek sent out two riders in the breakaway so they'd be available to escort Schleck in case he could shake his rivals.

With 56.6 kilometers left in the stage, Schleck chiseled out a lead of more than a minute against the contenders and caught his teammate Joost Posthuma, one of the breakaway riders who welcomed Schleck into his wake to go up Izoard.

Schleck crossed the top alone, still behind the rest of the breakaway but about 2½ minutes ahead of Evans, Voeckler and Contador. On the downhill -- not one of Schleck's strengths -- Schleck caught up with Belgian teammate Maxime Monfort, who slowed down to escort him.

With about 40 miles left, nearing the foot of the final climb, Schleck and four other breakaway riders caught Maxim Iglinsky of Kazakhstan, who had ridden solo at the front for much of the stage.

At the foot of 14-mile Galibier ascent, Schleck and the five others in the breakaway had extended its lead to 3½ minutes ahead of the pack.

With more than six miles to go, Schleck was continuing to gain time and was ahead by nearly 4½ minutes. Evans then admirably stayed at the front of the chase group for the rest of the climb and stage and in solo fashion managed to reduce Schleck's lead to a size which Evans will be able to erase in Saturday's individual time trial.

No other rider in the chase group helped Evans in his chase efforts and he again today showed why he deserves to be on top of the podium in Paris this coming Sunday. Not even the teams who were represented by more than one rider in the group or the GC contenders who had their lieutenants with them offered any help to Evans.

"When Voeckler and his team stopped riding and he has the yellow (jersey), it was a bit bizarre and strange," Evans told Roadcycling.com and Roadcycling.mobi after the stage finish and added "They've been riding a lot all week, but he had a teammate in the end, too. They sort of looked at me to do the work, but I was alone, too. I'm never happy to lose places on GC."

With about five miles left, Schleck was alone with Iglinsky close on his rear wheel. But he moved away from the Kazakh to ride alone, gritting his teeth and spitting water slurped from his bottle.

Friday's Stage 19 features two more "beyond category" climbs. They are up the other side of the Galibier, which wasn't covered Thursday, and the finish at the Alpe d'Huez after a 68-mile trek from Modane.