Lance Armstrong has grabbed the Tour de France by the scruff of the neck, outlasting his main rivals and charging from sixth into second place overall.

The American finished a close up second to stage winner Ivan Basso of Italy after an outstanding climb on the first major mountain stage in the Pyrenees ski resort of La Mongie.

The duo came home 20 seconds clear of Germany's Andreas Kloeden well ahead of major rivals including Iban Mayo (63 seconds behind) and Germany's 1997 winner Jan Ullrich (2:30).

Italian Basso was the only rider able to keep up with the charging Armstrong in the final gruelling climb of the 12th stage, finishing just ahead of the American in the same time.

"Ivan was the strongest today. I didn't give it to him," said Armstrong, who won at La Mongie two years ago.

"I don't think the Tour will be decided before Besancon," added the American, referring to the last time trial in the Tour next Saturday.

Five-times Tour champion Armstrong, bidding for a record sixth victory, now lies in second place five minutes and 24 seconds behind Frenchman Thomas Voeckler, who finished four minutes back and retained the yellow jersey.

"The mountain is always hard. But the pace is even harder here. When they accelerated, I couldn't keep up and I finished as best as I could," Voeckler said.

"I didn't see Armstrong. He dealt a big blow to the other guys' morale."

Armstrong, who had trailed by nine minutes 35 seconds at the start on Friday, streaked away from his main challengers on the climb where he took control of the Tour in 2002.

BIG CLIMBS

The Texan, along with his U.S. Postal team mates, picked up the pace on the two big climbs which made up the 199-km 12th stage from Castelsarrasin.

American Tyler Hamilton, fourth last year, was the first big name to lose ground six kilometres from the finish line while Armstrong's fierce rival Ullrich also drifted away.

"Jan isn't finished," Armstrong insisted. "He always starts slow and is a tough guy who never gives up."

Armstrong made his move with three kilometres remaining, CSC team leader Basso, who was seventh overall last year, the only rider to keep pace.

"I'm very happy. It's a very important result for me," said Basso, 26. "The Tour is still long and tough, but it's a good start. Lance is very strong but what matters to me is that my condition is fine," he added.

Saturday's 13th stage features another day of intense climbing on a 205.5 km ride from Lannemezan to Plateau de Beille.