By Matt Majendie
BBC Sport in Liege
Lance Armstrong thinks this year's Tour de France will be his most arduous yet.
Armstrong could make history in Paris
If the Texan takes victory, he will become the first man in the history of the sport to win the race six times.
Armstrong described German Jan Ullrich as his "biggest rival" but warned there were at least six or seven riders capable of winning.
"This is going to be my hardest Tour ever. Jan Ullrich is better prepared than we expected and better prepared than other years."
Among Armstrong's other rivals are former team-mate Tyler Hamilton, and Spanish duo Iban Mayo and Haimar Zubeldia.
Despite being wary about the task ahead, Armstrong said: "I feel good and I feel strong. I've had a high quality two weeks, which I needed as I had some work to do after the Dauphine Libere."
In the Dauphine, he finished a disappointing fourth and more crucially was outridden by both Hamilton and Mayo in the mountain time trial.
Arguably the biggest test for the US Postal team leader in the Tour is a similar 15.5km uphill race against the clock on Alpe d'Huez.
He has tipped Mayo to win the stage but still believes his team is strong enough for overall victory.
US Postal have a Tour novice in Benjamin Nodal, who replaces Victor Hugo Pena, one of Armstrong's key lieutenants in the mountains last year.
Of the decision, Armstrong said: "It's tough and bringing Benjamin in is a bit of a risk but one worth taking."
Should Armstrong take the yellow jersey on the Champs Elysees in Paris, he will exceed the efforts of fellow five-time Tour winners Jacques Anquetil, Eddy Merckx, Bernard Hinault and Miguel Indurain.
But he warned it was too early to talk about breaking records.
"If it happens that I'm wearing yellow come Paris, then we can talk about records. But this is a very tough test."
Many argue Tour organisers have produced a route designed to reduce Armstrong's chances of winning.
But the 32-year-old, who has been joined at the race by girlfriend Sheryl Crow, said: "I think the organisers make the event as interesting as they can.
"Whatever the route, I still believe the best man will win in Paris, and that's fine with me even if I'm second."