Floyd Landis reclaimed the yellow jersey in the Tour de France with fourth place in stage 15, L'Alpe d'Huez.
The American, riding for the Phonak team, took a 10-second advantage over previous leader Oscar Pereiro, who stays in touch in second overall.
The stage was won by Frank Schleck, who became the first rider from Luxembourg ever to win the famous stage by leaving Damiano Cunego behind with a late attack to take victory by 10 seconds.
Landis was not involved in the early breakaway, with Belgian Axel Merckx tasked with ensuring Phonak had a representative at the head of the field.
The race favourite made his move late in the piece, attacking along with fellow contenders Carlos Sastre, of Team CSC, and Davitamon's Cadel Evans to chase down the rapidly diminishing lead group.
And when he pushed for home on his own 10km out, only T-Mobile's Andreas Kloden was able to respond.
'The plan was to take as much out of the guys who were close to me as possible,' Landis told Eurosport.
'My job was to follow Kloden, and I got the jersey back, so there you go.'
After Pereiro, the chasing pack of Cyril Dessel, Denis Menchov, Sastre, Kloden and Evans trial Landis by over two minutes, but he refused to write off any of his challengers.
'You never know what's going to go on in the final week,' he said.
'The time differences are not that big yet, and I wouldn't write any of them off. A bad day can change everything, I've just been lucky that the good days have come at the right time.'
The result provides a huge psychological boost for Landis' hopes of winning the Tour, with L'Alpe d'Huez historically a significant marker.
On 20 of the 25 previous occasions the stage has featured in the event, the holder of the yellow jersey at the summit has gone on to claim overall victory.
In recent years, that man has twice been Landis' compatriot Lance Armstrong, who said: 'I would love the jersey to stay in America and that means Floyd. I think he's still the favourite, and I would be happy with that victory.'
The 30-year-old will also take confidence from the fact that he was able to leave Sastre, Evans and Davitamon Rabobank's Denis Menchov - another of the leading contenders - trailing in his wake in the closing stages.
David de la Fuente took 28 climbing points on the earlier ascents at Col d'Izoard and Col du Lautaret to take a commanding lead in the King of the Mountains standings, Schleck moving second on 74 points, 34 behind the Spaniard.
Another significant development was the withdrawal on the Col du Lautaret of Quickstep's Tom Boonen, who was lying second in the sprint category. Davitamon's Robbie McEwen now leads the race for the green jersey by 45 points from Oscar Freire of Rabobank.
Leading positions in stage 15 Gap - L'Alpe d'Huez (187km):
1 F Schleck Lux Team CSC 4hrs 52mins 22secs
2 D Cunego Ita Lampre-Fondital at 0.11secs
3 S Garzelli Ita Liquigas at 1.10
4 F Landis USA Phonak
5 A Kloden Ger T-Mobile all same time
6 R Lobato Spa Saunier Duval at 1.14
7 S Chavanel Fra Cofidis at 1.18
General Classification after Stage 15:
1 F Landis USA Phonak 69:00:05
2 O Pereiro Spa Caisse d'Epargne at 0.10secs
3 C Dessel Fra AG2R-Prevoyance at 2.02
4 D Menchov Rus Rabobank at 2.12
5 C Sastre Spa Team CSC at 2.17
6 A Kloden Ger T-Mobile at 2.29
7 C Evans Aus D-Lotto at 2.56
