Three-time champion Alberto Contador insists he is mentally tough enough to defend his Tour de France title under the intense pressure and scrutiny of an ongoing doping case.

The Spaniard begins his quest for a fourth win tomorrow, having been cleared by the Spanish cycling federation after testing positive for the banned anabolic agent clenbuterol late in last year's race.

The International Cycling Union and World Anti-Doping Agency have appealed the ruling to the Court of Arbitration for Sport.

Should they win, Contador faces the strange prospect of losing his 2010 title days after winning another one. "The pressure is not only on the road but also outside of it, there is more and more and I am conscious of that," Contador said yesterday.

"To focus on the race is something I've been used to doing now for many years. I have no problem with that."

The 28-year-old Contador is not easily fazed, whatever the scenario, and has a ruthless streak essential to champions.

He rode on the same team as Lance Armstrong on the 2009 Tour, withstanding intense pressures within that team to beat the seven-time champion and clinch his second Tour win.

Last year, Contador was locked in an intriguing duel with Luxembourg rider Andy Schleck, a race that went all the way through the mountains and turned in Contador's favor after some thrilling tussles in the climbs.

Criticized

Contador coldly chose not to wait when Schleck had a mechanical problem with his bike during a key climb. He was criticized for showing a lack of sportsmanship, but it ultimately settled the race.

But the thrill of that steely-eyed win was shortlived as the cloud of doping suspicion soon hovered over Contador.

Weeks later, results showed a positive test for clenbuterol on the second rest day of last year's race, and traces of the drug were found in tests performed over the next three days.

Spain's cycling authorities dismissed those tests because clenbuterol takes several days to leave a person's system, accepting his explanation that he inadvertently consumed very small doses of the substance in contaminated beef.

Flanked by Saxo Bank team boss Bjarne Riis and his teammates yesterday, Contador gave a curt answer to a question pertaining to the doping suspicions surrounding him, and whether he should be allowed to race.

"I always said very clearly that I am always against doping, zero tolerance, but you can think what you like," he said.