Cycling: Armstrong camp identify three main rivals for Tour

Johan Bruyneel, Armstrong's tactical adviser on each of his six Tour de France wins, picked Alexandre Vinokourov, Jan Ullrich and Ivan Basso as the competition. Of the trio, only Germany's Ullrich has ever won the Tour – in 1997 – while Basso and Vinokourov have filled third place the past two years. "I think those three are the real challengers," Bruyneel said.

Vinokourov is not as quick as his T-Mobile team-mate Ullrich on time trials, but better in the mountains than the muscular German – a famously slow starter. At the Dauphiné Libéré tune-up earlier this month, Vinokourov won the climb up Mont Ventoux, beating a tired-looking Armstrong by 37 seconds.

Although the Team CSC rider Basso lacks speed, he is a tenacious climber, as he showed on last year's Tour.

"He was the only one to stay with Lance in the mountains," Bruyneel said. "Will he be able to maintain his condition for three weeks on the Tour? That's the question mark. But it's possible."

Vinokourov's penchant for attack caused Armstrong problems in the mountains in 2003, when the Texan beat Ullrich by just over a minute – his smallest overall margin of victory.

Bruyneel admires the Kazakhstan rider Vinokourov, but believes his attacking range will be less this year.

"He takes advantage of every opportunity. I think he's become more resistant over the years, and stronger in the mountains," Bruyneel said. "In 2003, he wasn't one of the favourites, so he got some freedom to attack. I don't think it will be the case this time."

Ullrich, a five-time Tour runner-up, has long been considered Armstrong's main rival. But a poor showing last year – when he finished 8min 50sec behind Armstrong in fourth – has raised doubts about his commitment and ability to handle pressure.

But Bruyneel does not rule him out. "He is one of the best time-trialists and always gets better in the second half of the Tour," Bruyneel said. "He is definitely weaker in the mountains, but he is a tough guy who never cracks."