LA MONGIE, France -- Lance Armstrong took a big step toward a record sixth straight Tour de France crown on Friday by surging past key rivals on the first climb in the Pyrenees.
The Texan moved from sixth to second in the overall standings following a ride in which he was runner-up to stage winner Ivan Basso of Italy.
Jan Ullrich, Tyler Hamilton, Iban Mayo and Roberto Heras were among the pre-Tour contenders whose hopes of dethroning the five-time champion faded as Armstrong powered up the ascent ahead of them.
Riders started the 12th stage under blazing sunshine, then got doused by rain before emerging into sunny weather again on the last of two major climbs on the 122.7-mile trek from Castelsarrasin to the La Mongie ski station.
"It was a great day, especially with the weather," Armstrong said. "First the heat, then the thunder, then the sun again. For the overall standings it is great."
But he wasn't ready to declare victory over Ullrich, his German challenger. Another Pyrenean stage, the Alps and a final time trial await before the July 25 finish in Paris.
"Jan's not finished," Armstrong said. "He starts slow and he's a tough guy who doesn't give up. He might have taken one on the chin today but he always comes back and is strong in the last week."
Ullrich, the 1997 Tour winner, lost 2 minutes, 30 seconds to Armstrong -- a major setback. Hamilton gave up 3:27 while Heras was 2:57 behind. Iban Mayo of Spain was 1:03 back.
"I am disappointed today, of course," said Ullrich, a five-time Tour runner-up. "It was actually going well until the rain. But I have a good team and we are not giving up."
Armstrong's merciless performance on the ascent to the La Mongie ski station showed he will be hard to beat.
"Armstrong is the strongest man on this Tour," Basso said. "I think he's still got gas in his tank."
Armstrong is 5:24 behind French champion Thomas Voeckler, who struggled in the mountain stage but limited the damage by holding the yellow jersey.
Voeckler had been leading Armstrong by more than nine minutes before the grueling stage. He placed 41st on Friday, 3:59 behind Armstrong and Basso.
Armstrong is eyeing the second Pyrenean stage Saturday as another chance to further bury his rivals. If he triumphs and they falter again, the 127.7-mile route from Lannemezan to the Plateau de Beille could prove decisive for Armstrong.
"He stunned the favorites a bit today," said French rider Richard Virenque, who was 3:27. "Tomorrow, I think he's going to strike a sword blow on this Tour."
Basso, considered a possible future Tour winner, won a stage for the first time in his career. The 26-year-old cyclist captured the white jersey as the best young rider in 2002, when he placed 11th overall. He was seventh last year and hopes to win the showcase race in two to three years.