LES DEUX-ALPES, France -- Colombian rider Santiago Botero claimed his second stage victory of this Tour de France by winning Tuesday's 15th leg, the longest of the three-week competition.

Stage 15 -- At a glance

Stage 140.4 miles from Vaison-la-Romaine in the southern Provence region to Les Deux-Alpes, a ski station. It's the longest stage of this year's race. Winner Santiago Botero of Colombia, in 5 hours, 55 minutes, 16 seconds. How others fared Three-time champion Lance Armstrong retained the overall lead despite finishing the stage in ninth place, 6:41 behind Botero. Armstrong's lead over second-place Joseba Beloki in the overall standings was unchanged at 4:21. Quote of the day "He's just a young guy. He was at a disco and did a stupid thing.'' -- Armstrong on absent rival Jan Ullrich, who drew a six-month ban Tuesday for taking amphetamines. Ullrich said he took pills at a nightclub and wasn't trying to cheat. Next Stage 111.3 miles from Les Deux-Alpes to La Plagne, featuring three exceptionally difficult climbs. It is expected to be the toughest stage of the Tour.

Lance Armstrong finished 6 minutes and 41 seconds off the pace, but his big overall lead was unchanged and he remained on course for a fourth straight Tour title when the race finishes Sunday.

The Texan crossed the line just behind his main rival, Spain's Joseba Beloki, who surged ahead in the final few hundred yards. Armstrong was surprised, but caught up quickly and clocked the same time as Beloki.

"Les Deux-Alpes, it's too special,'' Armstrong said. "It's not too hard, it's not good for attacking.''

It's expected Armstrong will try extending his 4:21 lead over Beloki in Wednesday's stage from Les Deux-Alpes to La Plagne, which features three exceptionally difficult climbs.

"It's a lot harder,'' Armstrong said of the upcoming stretch, considered the hardest of the entire Tour. "It's not the same as today.''

Botero timed 5 hours, 55 minutes and 16 seconds in Tuesday's 140.43-mile run from Vaison-la-Romaine in the southern Provence region to this ski station in the Alps. He took the lead some 99 miles before the finish and never dropped back.

"I kept my rhythm the whole day,'' said Botero, who also won the ninth stage, an individual time trial. "Two days ago, I had a bad day. Sometimes, you have off days.''

The Kelme rider, known for his inconsistency, finished more than 15 minutes behind winner Richard Virenque in Sunday's stage to the Mont Ventoux. After Tuesday's leg, he was seventh in the overall standings, 11:31 behind Armstrong.

Belgian rider Mario Aerts was second on Tuesday, 1:51 behind Botero, and countryman Axel Merckx was third, 2:30 off the pace.

French rider Christophe Moreau dropped out after crashing early in the stage and cutting his lip. The Credit Agricole leader, who placed fourth in the Tour two years ago, had a string of crashes in the first week and was 41st overall when he quit.

Although Tuesday's stage was the first in the Alps this year, it was easier than the opening two mountain stages in the Pyrenees, and easier than the race to the top of the Mont Ventoux. It was expected to be much easier than Wednesday's 111.29-mile stretch.

The 20-stage Tour finishes on the Champs-Elysees in Paris on Sunday.