Lance Battles for 8th Tour de France Crown

Seven-time Tour de France champion Lance Armstrong may be poised for a comeback. As he entered the grueling athletic event's seventh stage, he trailed the race's overall leader, Fabian Cancellara of Switzerland, by a fraction of a second.

The competition heads into mountainous terrain today. It's a section where climbers thrive and just happens to be Armstrong's specialty. But is he ready?

"I think so. I feel good," Armstrong said. "Not sure exactly what to expect, but I'm optimistic."

The field faces a 139-mile haul from Barcelona to Andorra, with a physically draining uphill finish, the first and hardest of three days in the Pyrenees.

The course features the Serra Seca pass and a finish into Arcalis in Andorra that's so tough it's beyond classification in cycling's ranking system.

The three week tour has 21 stages.

During his long championship reign on the Tour, Armstrong always made his mark through the mountains, steadily gaining on competitors while keeping an eye over his rear wheel.

Falls Slow Armstrong's Tour

This year's competition hasn't been so easy. Two spills marred the last six miles of the 37-year-old's race. One involved Yukiya Arashiro of Japan and the other involved former world champion Tom Boonen of Belgium.

Armstrong was even overheard calling this last day "stressful."

But, 3½ years after his retirement, Armstrong has proved he can hold his own, though onlookers wonder if he still has the legs to climb.

Armstrong Attempting What Hasn't Been Done

To racing analyst Frankie Andreu, a potential comeback win would be remarkable.

"Nobody has ever taken three years off a sport and come back at a high level, much less try to win the tour," Andreu said.

For this next stage, Armstrong said the riders to watch are Andy Schleck, and his brother Frank Schleck. Another aggressive competitor, Alberto Contador, comes out of Armstrong's own Astana team. Contador won the Tour in 2007 and is known to be a strong climber. He's just 19 seconds behind Armstrong.

There will be one more challenging climb that could either set Armstrong apart from the pack or test his aging legs and it comes the day before the July 26 finale in Paris. It features an uphill finish on Mont Ventoux, which isone of cycling's most legendary climbs.

The Associated Press contributed to this story.