French rider Cyril Dessel won the 16th stage for his first stage victory in this race. He led a breakaway group of four to a downhill finish, completing the 98-mile trip from Cuneo, Italy, in 4 hours, 31 minutes, 27 seconds.
Schleck refrained from attacking during the mountain climbs, choosing to stay with his closest rivals. He finished 1 minute, 28 seconds behind Desseland gained ground on two rivals -- Russia's Denis Menchov and Christian Vande Velde, an American contending in a major three-week race for the first time.
A more decisive performance could come Wednesday, when the Tour's toughest stage ends with the storied serpentine climb to L'Alpe d'Huez.
"We're going to try to make the other riders lose the Tour de France tomorrow," Schleck said.
His main title rivals finished in the same time as Schleck. Bernhard Kohl of Austria remains second overall, seven seconds behind, and pre-race favorite Cadel Evans of Australia is third, eight seconds back. Carlos Sastre, a CSC teammate of Schleck, is fourth, 49 seconds behind.
Evans may have been the biggest winner Tuesday. The Australian would be content to stay eight seconds behind Schleck through the mountains, then blow his rival away in the final time trial Saturday. The race ends Sunday in Paris.
"I'm very happy because it would have been too tough to do tomorrow's stage with the yellow jersey," said Roberto Damiani, sporting director for Evans' Silence-Lotto team. "Evans is only eight seconds behind, but the pressure is still on CSC right now."
Menchov and Vande Velde had trouble on the concluding descent. Menchov simply couldn't keep up with the other race leaders, while Vande Velde fell.
"Nothing special happened," Menchov said. "I just lost the wheel. The upper sections of the downhill were very technical and difficult. ... I didn't panic and I didn't get scared, I just wanted to get down the mountain as safely and as fast as possible."
Menchov lost 35 seconds and dropped from fourth to fifth overall, 1:13 behind. The damage for Vande Velde was far greater, with the Chicagoan losing 2:36 and dropping from fifth to sixth in the standings.
"I just hit a tight corner and fell," said Vande Velde, who had already lost 35 seconds to the other leaders on the final climb up the Bonette-Restefond pass, a 16-mile uphill stretch.
Menchov and Vande Velde were not the only riders who had trouble going downhill.
South Africa's John-Lee Augustyn was the first over the Bonette-Restefond peak, but he skidded off the road on a turn onto a rock-strewn mountainside. A spectator had to help up to the road before he rejoined the race.
The day's first climb, the 13-mile Lombarde pass, brought the race back over the border into France. There will be even more climbing in Stage 17 Wednesday: a 131-mile ride featuring the fabled Galibier and Croix de Fer passes before the finish at L'Alpe d'Huez.
"With a stage like that looming, I think everyone had that thought in their minds today," Damiani said.
CSC team director Bjarne Riis relishes the pressure, and no doubt he remembers the last rider to win at L'Alpe d'Huez two years ago: Schleck with a solo attack.
"Tomorrow is a big day," Riis said. "You need to attack when the possibility is there. Today we couldn't do it, so we will have to do it tomorrow."
Associated Press writers Jamey Keaten and Jerome Pugmire contributed to this report.