LUXEMBOURG -- Three-time Tour de France champion Lance Armstrong still gets nervous about cycling's premier race.

"Anybody can win. Well, not anybody -- but almost anybody,'' Armstrong said on Thursday in Luxembourg, where the grueling 21-day race gets under way Saturday. "I'm not guaranteed to be in the front.''

"There could be somebody better, there could be 10 people better, and I know that,'' he said. "That's why I work hard, that's why I train hard and prepare hard, and that's why I still get nervous before the Tour de France.''

The U.S. Postal rider is highly favored to win a fourth consecutive Tour victory, in part because several of his top rivals will be missing. He would be the first American to win four tours: compatriot Greg LeMond also won three. The tour record is five wins.

Armstrong spoke a day after confirmation came that Jan Ullrich, last year's runner-up and winner of the 1997 Tour, tested positive for amphetamines in a recent out-of-competition surprise test. Ullrich is skipping the Tour because of a knee injury.

"It's unfortunate for him (Ullrich), it's unfortunate for his team, and it's unfortunate, really, for cycling,'' Armstrong said at Thursday's news conference, declining to comment further until the testing of additional lab samples is completed.

The 1998 Tour champion Marco Pantani failed to qualify for this year's Tour due to lack of form, but he is also embroiled in doping charges.

Armstrong is no stranger to doping suspicions himself. But a 19-month French doping probe into his U.S. Postal Team hasn't turned up any evidence of wrongdoing, and is expected to be closed later this summer.

This year has added significance for Armstrong. Although he didn't mention the words "Sept. 11,'' the terror attacks were clearly high on his mind, especially on the national Independence Day holiday.

"I imagine we all feel a little bit more American today than we did the last Fourth of July,'' he said.

As for security concerns, Armstrong said he'd asked Tour de France director Jean-Marie Leblanc earlier this year about increasing security for the event. Following coordination between French police, tour organizers and the U.S. State Department, Armstrong said, "We feel safe.''

Armstrong did not specify what kind of threat he might be concerned about.

"It's a huge sporting event, it's a great sporting event, contested on a global stage,'' he said. "If you compare it to World Cup soccer or the Olympic Games or the Super Bowl, or anything else, there is tremendous security at those events.''

"It was logical to me, with all this money and all of this attention involved, that we have some security,'' he said.

He acknowledged that a race that covers so much territory makes security hard, though.

"It is an event for the people, so it has to stay that way,'' Armstrong said. "But there is a way to be aware, and to be sharp, about potential hazards.''

With Ullrich and Pantani out, Armstrong said his main challengers included Spanish team ibanesto.com, whose strong climbers and time-trial racers Armstrong described as "scary.''

The 2,034.8-mile Tour takes riders through Luxembourg, Germany, the plains of northern France, the Mediterranean coast and the Pyrenees and Alps mountains. It's the shortest ever Tour, and is designed to keep the outcome uncertain until the last few days.

"Every year, they try to make the course more challenging for the past winner,'' Armstrong acknowledged. "Certainly I didn't take it personal that the mountains were late.''

Still, despite the early butterflies, Armstrong is confident that his team has gotten stronger.

"We've added three new riders, which I think has added to the strength of the team,'' he said. "The guys seem to be in good form right now.''