American rider George Hincapie won the 15th stage of the Tour de France held over 205km from Lezat-sur-Leze to the summit finish of St Lary Soulan in the Pyrenees.
Hincapie's Discovery Channel team-mate Lance Armstrong retained the yellow jersey he is aiming to win for a seventh consecutive time before retiring after the race on July 24.
The race will resume with a third and final day in the mountains following Monday's rest day.
On what was the second of three days in the Pyrenees, and with six major climbs the toughest stage on the race, Armstrong's challengers were never going to launch an audacious attack too early.
It was no surprise that when a group of 14 riders formed after an early attack by Dutchman Michael Boogerd they were allowed to build a solid lead, which hit a maximum of 18 minutes.
But as they stage leaders slogged their way over the first of the day's climbs, the searing temperatures and continuous effort began to take their toll.
One by one the 14-man group began to thin out until only six riders rode over the summit of the Peyresourde - the fourth Col of the day - with a 12-minute lead on Armstrong's group, which in turn was also beginning to break up.
Behind them Ivan Basso's Spanish team-mate Carlos Sastre, Australian Cadel Evans and France's Christophe Moreau were dropped and they were soon joined by Liberty duo, Jorg Jaksche and Alberto Contador.
Jaksche and Evans managed to rejoin the chasing peloton a kilometre before the summit. It was a wise decision given the two difficult climbs still remaining.
The leaders had lost four minutes to the peloton on the Peyresourde climb, and on the subsequent 7.5 km climb to Louron-Azet the pace of Armstrong's team thinned out their group.
The first significant attack came from Basso, who pulled away from Armstrong, who soon followed the Italian. Both briefly distanced Jan Ullrich but the German managed to grapple his way back.
His T-Mobile team-mate Alexandre Vinokourov was left trailing and ended up in the small group which was being led by the race's best climber, Michael Rasmussen, in a bid to keep in touch with the trio.
Armstrong, Basso and Ullrich came over the Louron-Azet summit with a 7:40 deficit on the six leaders, who had already began the tricky 18km descent towards the day's final climb in earnest.
At the front meanwhile Oscar Sevilla's attack on the first kilometres of the final climb was countered by Oscar Pereiro. The former was left trailing as his Spanish compatriot raced with Hincapie and Boogerd towards the summit finish.
Hincapie looked the freshest, given his lack of relaying the lead group for most of the day - and again the New Yorker was happy to sit on Pereiro's wheel for the 10.7km final ascent.