Armstrong, going for a record seventh straight Tour victory before he retires, finished in the same time as Boonen and kept his grip on second in the overall standings. American David Zabriskie retained the yellow jersey as the leader.

Armstrong resumed his strong pace after delivering an early blow to his rivals Saturday, placing second in the opening time trial.

"My legs were terrible," Armstrong said, joking. "Actually, I feel pretty good. I figure the faster I pedal, the faster I can retire."

Although Armstrong wasn't looking to win, he was nervous. Flat stages favor sprinters, meaning there is often a rush to the finish in which riders can crash.

"Everybody's a bit nervous, everybody's cracking a little bit," Armstrong said. "These finishes still scare me. I won't miss them."

Boonen won the 112.5-mile ride from Challans to Les Essarts in 3 hours, 51 minutes, 31 seconds, just ahead of Norway's Thor Hushovd, who posted the same time. Australians Robbie McEwen and Stuart O'Grady were third and fourth.

"It was a sprint for the strong riders, so it was an advantage for me," Boonen said. "It was not a problem."

Armstrong's main rival, Jan Ullrich, failed to gain on him, but his 19th-place finish was an improvement on Saturday's time trial.

Although the German is still feeling the effects of crashing through the rear window of his team car during training Friday, Armstrong believes Ullrich remains a serious threat.

"I talked to him today," Armstrong said. "If you go into the back of the car and shatter the window with no helmet on, that's got to affect you. So you can't take anything away from him after the way he rode yesterday. He'll be better in a few days time."

Ullrich said he woke up