Namur, Belgium ? Lance Armstrong has no doubts about the risks that lurk in the next stage of the Tour de France: If luck goes against him, he says, his drive for a record sixth straight win could be over almost before it’s begun.

One of the obstacles for the five-time champion will be bone-shaking cobblestone paths that some riders say shouldn’t even be part of cycling’s showcase race.

The paths are bumpy, unsettling and treacherous when wet — in short, a recipe for crashes.

“Everybody is worried,” the Texan said Monday. “It’s always dangerous. You have to be in the front. If you get stuck behind a crash or something like that, then you could almost say that your Tour is finished.”

Armstrong is fourth overall, 18 seconds behind overall leader Thor Hushovd of Norway. He finished 85th in Monday’s 122-mile second stage from Charleroi to Namur in Belgium.

So far, Armstrong seems pleased, saying his team “is maybe the best one we’ve had.” But the competition is perhaps the toughest he has faced.

“The field is full,” said Armstrong, who won’t look to take the lead until later in the three-week race. “The course is tough, but I think the competition will be deeper than other years.”

Armstrong’s biggest rival, 1997 Tour winner Jan Ullrich, is a mere 15 seconds back. He finished 38th in the second stage, with the same time as Armstrong.

The two cobblestone sections today come in the second half of the flat 130-mile stage from Waterloo to the northern French town of Wasquehal. They are fueling worries after two nervous days of crashes and high-speed sprints.

The relatively flat early stages provide a chance for glory for sprinters who have no hope of winning the Tour title when it ends July 25 in Paris.

The speedsters include Australia’s Robbie McEwen, who dashed to victory in a mass sprint at the end of Monday’s stage.

In finishes like that, Armstrong and the other riders who wait until the mountain stages to make their move do their best to avoid spills.

The first cobblestone section today runs for 1.7 miles. The second, 15 miles from the finish, is nearly three-quarters of a mile long and also forms part of the Paris-Roubaix race, a grueling classic known as “The Hell of the North.”