With a doping case still hanging over him, Tour de France winner Alberto Contador will begin the 2011 Giro d'Italia this weekend as the overwhelming favorite in what he calls the "most difficult race I have ever faced."

The Giro starts Saturday with a team time trial in Turin, Italy. After 19 brutal stages, it concludes with an individual time trial in Milan on May 29

"At the start of the season after talking with the team we decided to focus our attention on this race," said Contador, who has already won the Volta of Catalunya and Vuelta of Murcia.

"It will be the most difficult race I have ever faced," Contador said. "My objective is to have the pink jersey on the final day or at the least be in contention for it."

Contador, who tested positive for clenbuterol while winning last year's Tour de France, was cleared by the Spanish cycling federation after he blamed the result on contaminated beef.

Cycling's governing body and the World Anti-Doping Agency have appealed to the Court of Arbitration for Sport, which is expected to issue a ruling before this year's Tour.

"I prefer not to think about that and only concentrate on sporting matters," Contador said. "The hearing with CAS is still in the future. I have total trust in the people that work for me and that we will get a favorable verdict."

Contador, the winner of the 2008 Giro, said Spanish Vuelta winner Vincenzo Nibali will be his main challenger after defending champion Ivan Basso dropped out of the race.

"He has made a step up in class over the last two seasons," Contador said. "He did well in the 2009 Tour, then last year he was the last rider called up for the Giro d'Italia and finished third.

"Then he won the Vuelta with great consistency, which shows how much he has matured. For me he is the favorite. He is a good racer and has spent the whole season thinking about the Giro."

Another Italian expected to challenge is Michele Scarponi. He finished fourth in 2010, and since changed teams from Androni to the more powerful Lampre.

"Contador is stronger than me but we are starting from the same point," Scarponi said. "I want to be competitive in this Giro until the very end. This year I have prepared better. I feel more mature and I know myself better. Furthermore, I am in a stronger team and we are ready."

Meanwhile, HTC-Highroad sprinter Mark Cavendish will be aiming for the sprint stages after winning the green points jersey in the 2010 Vuelta a Espana.

"I'm been pretty solid all season," he said. "Throughout the year I've been in solid form. I'm not at the stage I'll be in the Tour, but I am pleased with how I'm feeling."

In total, the Isle of Man rider and one of the world's top sprinters has won five stages at the Giro, but the last of those was in 2009 after he missed last year's race.

"This is my favorite event, because the whole team gets to celebrate, so the whole team has to do it right," Cavendish said. "So as long as we get on the podium, it isn't really important who gets the jersey.

"Like with every Grand Tour, one win constitutes success. If you don't go away with one win, you've failed," he said. "You have to try for every stage. I'll be trying for the five sprint stages and we will try to win the team time trials."

Nine of the stages are rides of over 125 miles, while three have climbs of over 6,560 feet.

"It's just going to be mad," Team Garmin-Cervelo rider David Millar told press representatives and continued "The course is bananas. It's all over the place and ridiculously difficult. Then we have these transfers that are, again, catastrophic at times.

"It's very demanding, physically and psychologically, for everyone involved. It's exhausting from all angles. It'll be a good race, I think, because Italy will be behind Nibali and you'll have Contador there who's the world's best stage-race rider."

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