LE GRAND-BORNAND, France, July 22, 2009 (AFP) - Spain's 2007 champion Alberto Contador tightened his grip on the Tour de France yellow jersey here on the race's 17th stage Wednesday as the peloton waved goodbye to the Alps.

Luxemburger Frank Schleck won the stage after he and younger brother Andy were left to race with Contador from the summit of the day's fifth and final climb, the Col de la Colombiere, towards the finish.

Although rivals, the trio made huge benefits in working together.

The Schlecks moved up the overall standings to drop Britain's Bradley Wiggins off the virtual podium, one of the reasons why Contador apparently chose not to dispute the stage win.

While the stage win for Saxo Bank is welcome, especially after they lost close teammate Jens Voigt to a serious crash on Tuesday, the Schlecks will take more pleasure from their jump up the race's general classification.

Contador now leads Andy Schleck by 2min 26sec overall, with brother Frank moving up to third at 3:25 behind the Spaniard.

Lance Armstrong meanwhile kept his promise to support teammate Contador's cause, staying behind to mark potential rivals when the Spaniard counter-attacked the Schlecks on the Col de Romme.

The 37-year-old American, the seven-time champion, came in around two minutes adrift to drop from second overall at 1:37 to fourth at 3:55 behind Contador.

He admitted he is now racing the Schlecks for second place.

"If I don't win it's not the end of the world, but of course I would like to be on the podium in Paris," said the American.

Astana teammate Andreas Kloden is fifth while Wiggins, arguably the day's biggest loser, dropped from third to sixth at 4:53.

"We had nothing to lose this morning," said Frank Schleck, who took his second stage win on the race and first since winning at Alpe d'Huez in 2006.

"We staked everything on launching those attacks. It was a bit risky but at the end of the day you have to take risks to benefit."

On the third and last, and most difficult, day of climbing in the Alps Contador confirmed his status as the undisputed race leader.

With the next big rendez-vous the individual time trial on Thursday, and with neither Schlecks known for their formidable time trialling skills, Contador's lead looks comfortable.

He denied he had deliberately collaborated with the Schlecks, but the Spaniard admitted their ride together had allowed him to put the threat of Wiggins, a time trial specialist, out of his mind.

"The Schlecks asked me to collaborate (to distance their rivals) with them but I said 'no' because I had teammates behind," said Contador.

"I just decided to stay in their wheel until the finish line. As it stands now, I think the gap on Wiggins is enough for the time trial."

Wiggins simply hopes he can give his best on Thursday.

"Today was hard. It was the first stage of multiple mountains I've ever contested for GC (general classification)," said a dispirited Wiggins.

The final major test of the Tour will be on the penultimate stage, which finishes with the 21 km climb to the summit of Mont Ventoux.

But given the ease with which he is climbing, Contador looks unbeatable.

The 26-year-old Spaniard looked comfortable whenever the lively Schleck brothers accelerated on the difficult Col de Romme, whose summit was 29 km from the finish.

Thanks to their attempts a group containing all the top five in the general classification among others was split, with Armstrong left behind to mark Wiggins.

The Schlecks' fireworks however failed to frighten Contador, and with his Astana teammate Andreas Kloden staying with him, at least until the closing kilometres of the Colombiere climb, the Schlecks were running out of options.

With Contador apparently unbeatable, it would soon become clear that leaving Wiggins as far behind as possible was Andy Schleck's best option.

The quartet came over the summit of the Col de Romme with a 1:20 lead on Armstrong, Wiggins, his Garmin teammate Christian Vande Velde, and Italian Vincenzo Nibali of Liquigas.

And the gap continued to grow as the Schlecks and Contador finally left Kloden near the top of the Colombiere.

In their wake Armstrong decided it was time to up the pace and he left Wiggins trailing in the final kilometre of the climb.

Early in the stage pre-race contender Cadel Evans of Australia was struggling and finished well behind to drop to 37 minutes off the pace.

"Physically, I am not anywhere near where I was on a bad day. What can I do?" said Evans, the runner-up the past two years.

"I can kill myself for 25th place in the GC (general classification) or something, but I am not riding for that. My ambitions are much higher."