LOUDENVIELLE-LE LOURON, France -- Lance Armstrong is starting to consider what once seemed almost unthinkable: losing.
He still leads the Tour de France, but Jan Ullrich is a mere 15 seconds behind -- and a new threat emerged Sunday.
Alexandre Vinokourov of Kazakhstan pulled away from Armstrong in the day's last climb in the Pyrenees and trails by only 18 seconds in the overall standings.
Such a tight race is uncharted territory for Armstrong, who is trying to match Miguel Indurain's record of five straight Tour titles.
"It's obvious that I'm not riding as well as I have in the years past. I can't exactly say why," Armstrong said. "I'm still not 100 percent and when you're lacking and when you're missing form, you've just got to rough it."
Vinokourov started the stage 61 seconds back. Now he, Ullrich and Armstrong face a battle of wits and stamina with only six days of racing left before the finish in Paris.
Since three Alpine stages a week ago, Armstrong has complained about his riding and the crushing heat. Instead of his usual self-assurance there's struggle.
"Something's not going right and there's nothing I can do about that now," he said. "All I can do is wake up every morning and do my best. I'm not going to cry and whine. I'm just going to do my best."
Cutting his losses, Armstrong stuck with Ullrich on Sunday. He let Vinokourov power ahead up the 5,158-foot Col de Peyresourde pass, the last of six climbs that made this one of the hardest of four stages in the Pyrenees.
Vinokourov placed sixth in the 119-mile stage, 43 seconds ahead of Armstrong and Ullrich. They finished 11th and 12th, 84 seconds behind stage winner Gilberto Simoni of Italy. Ullrich's overall 15-second deficit to Armstrong did not change.
The three contenders face two more days in the mountains that separate France and Spain and an individual time trial to Nantes on Saturday, the day before the Tour ends.
"I knew it was going to be close," Armstrong said. "I probably didn't expect it to come down to the last few decisive stages -- two days in the mountains here ... and then the final time trial."
"If we get to Nantes and I have 15 seconds and I lose by 16, you know it will go down as the closest Tour de France in history and I'll go home and have a cold beer and come back next year," he added.
Monday's stage to Luz-Ardiden has two imposing climbs, and Vinokourov senses he can take the yellow jersey.
"It's still doable," the Team Telekom rider said. "It's always a dream. I believed I would today, but there remains another hard stage tomorrow."
But Armstrong still regards Ullrich, the 1997 Tour winner from Germany and four-time runner-up, as his key rival.
"He's strong, so you have to wait until you see a weakness or a weak moment, and so far I haven't seen that," the U.S. Postal Service star said. On the climb to Luz-Ardiden, "if I feel good I will probably attack," he added.
Armstrong said he felt better Sunday than a day earlier, when he was still recovering from a time trial on Friday in which Ullrich took a chunk from his overall lead.
"Yesterday was a bit of a crisis after the disaster of the time trial," Armstrong said. "Today was good. Tomorrow is important -- it's my big stage."
Simoni was timed in 5 hours, 31 minutes, 52 seconds in winning the 14th stage, a jagged route from Saint-Girons to Loudenvielle-Le Louron.
Simoni, this year's Giro d'Italia winner, was once expected to challenge Armstrong but has had a poor Tour. He became ill early on and his coach urged him to pull out Saturday.
"Today's win erases the fatigue and suffering of the past days," he said. "I am somebody who never gives up."