CAP'DECOUVERTE, France -- An exhausted Lance Armstrong is the first to admit it: He's no longer the man to beat in the Tour de France.

Parched and weak after a ride on a scorching day, the four-time champion ran out of energy -- and water -- on a key stage leading to the Pyrénées.

Breakdown -- Stage 12

Ullrich Stage Gaillac to Cap' Decouverte. A crucial 29-mile individual time trial with riders racing against the clock. Winner Jan Ullrich of Germany in 58 minutes, 32 seconds. Ullrich, the Tour's 1997 winner, closed within 34 seconds of overall leader Lance Armstrong. How Others Fared Armstrong, in his favorite discipline, finished second; Kazakhstan rider Alexandre Vinokourov was third; American Tyler Hamilton, competing with a broken collarbone, finished fifth; Spain's Iban Mayo was 12th. Yellow Jersey Armstrong retains overall lead of 34 seconds over Ullrich. Quote of the Day "I felt like I was pedaling backward.'' -- Armstrong, detailing how difficult he found the exhausting time trial. Next Stage Saturday's 13th stage has the riders returning to the mountains, with a 122.45-mile run through the Pyrénées from Toulouse to Ax 3 Domaines. The stage features a climb of 6,603 feet, called Port de Pailheres. -- The Associated Press

The Texan finished second in an individual time trial Friday and lost precious time to one of his main rivals -- stage winner Jan Ullrich of Germany, who moved into second place overall.

Not since Armstrong overcame cancer to return to the Tour in 1999 has his grip on cycling's most prestigious race looked so tenuous.

He barely kept the overall lead after a crucial time trial in which riders unleash every bit of force to beat the clock.

Armstrong did extend his overall lead from 21 seconds to 34, but he had been counting heavily on using this stage to distance himself from the field.

Instead, Ullrich is lurking.

Ullrich, a 1997 Tour winner and twice runner-up to Armstrong, powered across the 29 miles of rolling vineyards in 58 minutes, 32 seconds to take the Tour's 12th stage. He was the only rider of 167 to finish in less than an hour.

Ullrich, of Team Bianchi, shaved more than 1½ minutes from Armstrong's lead as the Tour enters the lung-wrenching Pyrénées.

"Now he's the big favorite,'' Armstrong said.

Armstrong looked stunned when he ascended the podium to accept the leader's yellow jersey. Afterward, he seemed spent -- physically and emotionally.

"I had an incredible crisis. ... I felt like I was pedaling backward,'' a flush-faced Armstrong said. Temperatures in the shade reached 97 and were far worse in the sun.

"Perhaps it was too hot for me,'' Armstrong said. "I don't know. I suffered.''

Armstrong lamented running out of water before the final climb to the finish line, set on a rocky outcrop that was once a carbon mine but later turned into a theme park.

"It's the thirstiest I've ever been in a time trial, right from the beginning for some odd reason,'' he said.

Ullrich, however, was absolutely buoyant.

"From the start I never thought I could win this time trial,'' he said, sweat dripping from his face. "I got my old rhythm back ... I didn't expect this (victory) myself.''

"I have never beaten Armstrong in a time trial in the Tour before, and I did it now, in my comeback year,'' he added.

More bad news for Armstrong: Ullrich tends to grow stronger as the race enters its final eight stages, four of those in the Pyrénées.

Armstrong did slightly widen his lead over Alexandre Vinokourov of Team Telekom, who placed third, 2:06 behind. The Kazak mountain specialist, who had been the nearest rival until Friday, trails by 51 seconds overall.

Armstrong was not the only exhausted rider. Immediately after crossing the finish line in fifth place, American Tyler Hamilton -- competing with a broken collarbone -- stumbled off his bike, lurched forward and vomited.

Hamilton was injured during a mass crash July 6 but persevered through the pain to carry on. The Team CSC rider is fourth overall, 2:59 behind the leader.

Since he won his first Tour in 1999, Armstrong has won six of eight individual time trials. Aside from Friday's race, his only other loss in the time trial came last year.

Talk of his vulnerability has dominated this race. And his latest performance provides a psychological lift to his opponents, who now see victory well within their grasp.

"It's a very difficult day,'' Armstrong said.

Armstrong is trying to join Spain's Miguel Indurain as the only cyclist to win five straight titles. Three others have won cycling's showcase event five times but not consecutively -- Bernard Hinault, Jacques Anquetil and Eddy Merckx.

As he prepares to lead the pack into the treacherous Pyrénées, Armstrong sounded less than confident.

"If the others attack in the Pyrénées, then I'll follow, or I'll try to follow,'' he said.

But one factor that could play into his hands is the unsettled weather that is expected to descend on the mountains this weekend.

"I saw the forecast for storms in the Pyrénées Sunday,'' Armstrong said. "So that was good news.''