But the Lance Armstrong who sets out tomorrow in search of a historic Tour de France crown is a man facing a mountain of pressure — from fame, fortune, family and a marriage that, by his own admission, he's struggled to keep together.

As competitors search for a weakness, the crucial question of this year's centennial Tour is whether the 31-year-old cancer survivor still has what it takes to win the world's most grueling sporting event.

The next three weeks will tell. For his part, a quietly confident Armstrong said yesterday that a record-tying fifth consecutive victory was far from certain.

In a race as long, punishing and unpredictable as the 23-day, 2,125-mile clockwise slog around France, almost anybody can win, he said.

"I think it will be a tighter race. I'm not getting any younger, and therefore probably not getting any stronger," Armstrong said at a news conference, his face tanned, his hair cropped short.

"Other guys are reaching the pinnacle of their career. I think there are some wild cards that can really change the face of the race."

Armstrong survived cancer, brain surgery and stomach-churning chemotherapy to return to cycling and win the Tour for the first time in 1999. Three more Tour victories have turned him into a sporting icon, bringing fame and commercial deals.

Despite all his appearances in TV ads and magazines, Armstrong's marketability has yet to reach its full potential, said Jim Andrews of IEG in Chicago, which publishes IEG Sponsorship Report.

"Even if he wins or loses and says, 'That's it,' he still has an incredible story and is potentially even more popular in retirement than as an active athlete," Andrews said.

According to his new book due out in October, Armstrong and his wife, Kristin, have had problems in their marriage. A spokesman for Armstrong's U.S. Postal Service team, Jogi Muller, said they are trying to sort them out. They have three young children.

"Life is more complicated and hectic now than it was three or four years ago," Armstrong said. "Until now I don't think that these complications have compromised the buildup, but the next three weeks will tell us if they have truly, because this is the pinnacle of our sport and the hardest moments we ever experience."

Armstrong's preparations for the Tour suffered in June when he fell from his bike during a mountain descent on the warmup Dauphine Libere race. While he was not seriously injured and went on to win the race, he finished the stage with rips in his shorts and a bandage on his right arm. Armstrong was surprised by how long it took to recover, but he also made clear he is ready for the Tour's rigors.

"I show up prepared, I show up motivated and I show up because I love it and I respect it and I want to do well," he said. "Nothing means more to me than to win this event.

"The race has everything. I think it has difficulty, it has joy, it has excitement, and it even has death," he said.

If he wins, Armstrong will join Spanish legend Miguel Indurain as only the second rider to capture five consecutive Tours. Indurain won in 1991-95. Three other racers have won five Tours, but none of them consecutively.

Other riders acknowledged that Armstrong is clearly the man to beat.

"He is the master of the arena. For that, we owe him respect. He's won four times, to win a fifth is harder," said Giro d'Italia winner Gilberto Simoni, one of Armstrong's main challengers.

The 198 riders start tomorrow from the foot of the Eiffel Tower. All the riders were given blood tests yesterday — part of efforts to prevent doping that has sullied previous races. All riders passed, cycling's governing body said.

Over the next three weeks, they will battle up seven leg-crushing mountain stages, sprint against the clock and ride long and hard across the French countryside. There's plenty of potential for the unexpected.

"When everybody talks about victory and what's going to happen, and what are you going to do, it gives me a mad feeling," Armstrong said. "Nothing is given in this sport, and anybody can win."

Armstrong announced yesterday that he would again ignore the protocol that the previous year's winner begins the race wearing the leader's yellow jersey. Organizers said while his stance was "unusual," it broke no rules.

The yellow jersey was first introduced in the 1919 race, to help crowds identify the race leader.