LOUDENVIELLE-LE LOURON, France &

The Tour de France is shaping up as a one-on-one between Michael Rasmussen and Alberto Contador. Not so much a street fight as a mountain fight.




With the Tour's toughest climb to come and a crucial time trial also ahead, neither has much margin for error.




"If I have a good day I will attack Rasmussen," Contador said.




The 24-year-old Spanish rider trails Rasmussen by 2 minutes, 23 seconds after Monday's 15th stage, a punishing ride along five climbs in the Pyrenees.




The wiry Dane reeled in repeated breakaway attempts by Contador, his last major challenger for the yellow jersey, and one-time race favorite Alexandre Vinokourov won the stage along the Spanish border.




The riders rest today, then it's back to the mountains for Wednesday's tortuous Pyrenean ascent.




Considering Rasmussen is two-time holder of the King of the Mountains jersey, a Contador comeback will be a tough task.




"I will try to attack the yellow jersey," Contador said. "If I get the chance."




The pair hold comfortable leads, with no rival closer than 1:37 behind Contador.




"I think it's just between them," said Erik Breukink, Rasmussen's sports director at Rabobank. "The time trialers are far back; (Andreas) Kloeden, (Cadel) Evans, (Levi) Leipheimer. I also think the Aubisque can widen the gaps."




The Aubisque pass will be the last of four enormous climbs on Wednesday. Heading into that, Rasmussen was 4:00 ahead of Evans; 5:25 ahead of Leipheimer; and 5:34 clear of Kloeden.




Vinokourov, who also won Saturday's time trial, won stage 15 in 5 hours, 34 minutes, 28 seconds.




Rasmussen, meanwhile, has deflected doping suspicions surrounding him as effortlessly as he conquers hills, and he is equally vigilant about what to expect from Contador.




"He probably has the best acceleration of anybody on the climbs," Rasmussen said Monday after withstanding three attacks from Contador on the final climb up the Col de Peyresourde.




Contador got to five wheel lengths ahead, but Rasmussen countered with assurance, if not ease.




"I was certainly under pressure, but luckily enough I managed to get back every time," Rasmussen said.




Rasmussen, 33, was dropped from Denmark's national team last week for failing to tell anti-doping officials of his whereabouts for drug-testing.




He missed two drug tests by the Danish anti-doping agency in May and June, and failed to respond to two warnings from the International Cycling Union since April 2006. A third infraction with either the UCI or the Danish agency would be considered equivalent to a positive test.




"The last thing this sport needs is more speculation about doping," UCI chief Pat McQuaid said Monday.




He added that Rasmussen has "broken no rules, so from that point of view ... you have to give him the benefit of the doubt."




Those comments did not bother Rasmussen in the slightest.




"That's new to me," Rasmussen said. "I certainly have no intention of giving up now."




Rasmussen was busy riding up the Col de Port shortly after noon when French customs officials stopped and searched his Rabobank bus &

along with those of the Discovery Channel, Team CSC and Astana.




The Astana bus looked gutted as officials checked even the undercarriage &

and asked one Astana employee to unfurl a huge toilet-paper roll.




Team CSC spokesman Brian Nygaard said the officials "asked to see the papers and the contents of the bus and what we had in our fridge. When you carry the things to the Tour for the riders, the vitamins, you need paperwork."




The Rabobank team shrugged it off.




"It's no problem for us. They can do a bus check every day &

we're concentrating on the race," Breukink said. "It's more important. When everybody talks about that (the Rasmussen case), everyone loses their morale."