LE GRAND-BORNAND: Alberto Contador used the third and final Alpine stage of the Tour de France to take a further step toward a second victory in cycling's showcase event.

The 26-year-old Spaniard, following another impressive run through the mountains, handed one more blow to his rivals when he tightened his grip on the yellow jersey by taking second place in Wednesday's 17th stage behind Frank Schleck of Luxembourg.

Four days before the race ends on the Champs-Elysees, Contador leads his closest challenger, Frank Schleck's younger brother Andy, by 2 minutes, 26 seconds.

Contador's Astana teammate Lance Armstrong, still aiming at a podium finish, dropped to fourth overall at the end of the 105-mile stage between Bourg-Saint-Maurice and Le Grand-Bornand. The 37-year-old Texan, who is set to announce plans for a new team for next season on Thursday, could not keep with the leading group in the grueling ascent to the Col de Romme.

Contador, only one of five men with a victory in the three Grand Tours — France, Italy and Spain — made a bold move when he tried to drop the Schlecks in the Col de la Colombiere, the last climb of the day. Contador's attack did not harm the brothers but it proved fatal to his Astana teammate Andreas Kloeden of Germany, who sits 4:44 back in fifth place.

Armstrong was quick to criticize the move on his Twitter feed.

"Getting lots of question why (Alberto Contador) attacked and dropped Kloeden. I still haven't figured it out either. Oh well," Armstrong wrote.

Tensions within the Astana team have been fierce since Armstrong announced his comeback last year and joined the squad managed by Johan Bruyneel, the man behind his seven victories on the Tour. The rivalry between the cancer survivor and cycling's new star Contador — who has been under contract at Astana since 2008 — reached new heights during the Tour.

Although Bruyneel said the Spaniard has almost secured victory, the Belgian was also prompt to question Contador's move.

"Today I told him several times that it was not necessary to attack to win the Tour," Bruyneel said after the stage. "I said it because we still have some hard days to come. It was his choice, it didn't work."

Astana sports director Alain Gallopin, the man who groomed Contador all season, was even harsher.

"He made a mistake. He made Andreas lose second place," the Frenchman told French radio Europe 1 on Wednesday evening.

While most teams would find no problem having Contador among their ranks, Armstrong's presence at Astana seems to weaken the Spaniard's position.

"We did not tell him to attack, he had won the Tour," said Gallopin. "He is a young rider, he still has to learn."

Armstrong and Bruyneel are expected to launch their new team together next year, while Contador has been linked to a move to Spanish outfit Caisse d'Epargne. Both riders are forced to live together for the next four days and are likely to face each other in next year's Tour.

"For now, we want to win the Tour de France, we are on the right path, then we will see," said Bruyneel.

As for this year, it seems Contador has bested his American teammate.

On the eve of Thursday's 25.2-mile time trial in Annecy, Contador sits on a comfortable cushion. Andy Schleck is 2 minutes, 26 seconds behind with elder brother Frank in third, 3:25 off the pace.

Bruyneel was confident Contador would maintain his overall lead.

"Tomorrow, the time trial will be good for Alberto because he is better than the Schlecks. Then, the Ventoux (on Saturday) and this is it. It looks good as far as winning the Tour is concerned. He is in great shape, he has never been in danger," he said.

Armstrong, fourth overall and 3:55 back, said a second place finish was still within his reach.

"Yes, it's still my goal, I think it's possible," he said. "I just need to work hard on the time-trial tomorrow ... We still have two big days."

After Thursday's mainly flat time trial, Tour hopefuls will tackle the daunting and feared Mont Ventoux — a nearly 7,000-foot ascent at an average gradient of 7.6 percent — during Saturday's penultimate stage.

Armstrong never won at the top of the Ventoux, a huge moonscape of rock in Provence with no vegetation, and he has previously said it was one of his biggest regrets.