Contador earned his third Tour de France victory in 2010
Tour de France winner Alberto Contador said he will appeal against his provisional one-year ban and insisted he was innocent of any doping offence.
The suspension, proposed on Thursday by the Spanish Cycling Federation (RFEC), was imposed after the 28-year-old tested positive for clenbuterol.
An emotional Contador told a press conference: "I'll appeal and defend myself to the last."
The Spaniard said contaminated meat was responsible for his dope test failure.
Contador added of the RFEC provisional ban: "I am against this proposal. I will work to cancel it but in case it becomes definite, I will appeal in every possible court to defend my innocence."
The rules give the Madrid-born rider 10 days to lodge an appeal if the ban is confirmed.
Should any appeal succeed, the sport's governing body, the UCI, and the World Anti-Doping Agency (Wada) have the right to challenge the decision.
Speaking at his team Saxo Bank's hotel in Majorca, Contador said: "I am an example for many people. I know what I am exposing myself to and for that reason I have never taken performance-enhancing drugs.
"I can say it openly and clearly and with my head held high, I consider myself an example of cleanliness."
Contador, who was close to tears throughout his statement, also appeared to back away from his previous threats to quit the sport if he was banned.
Asked whether he would leave cycling, he replied: "Right now I don't think so."
Saxo Bank team owner Bjarne Riis added that Contador had his support and also that of the team's sponsors.
A "very small concentration" of clenbuterol, a muscle-building and fat-burning drug, was found in Contador's urine sample on 21 July 2010, by an accredited laboratory in Germany.
The amount was 40 times less than the 50 picograms which the anti-doping laboratories accredited by Wada must be able to detect.
Contador, the yellow jersey winner in Paris, first in 2007 and then in 2009, could be stripped of the 2010 Tour title. The only previous Tour winner to suffer that fate was American Floyd Landis in 2006.
The Spaniard won last year's Tour de France by 39 seconds from Luxembourg's Andy Schleck.
Contador could be stripped of his Tour de France title
A UCI statement on Thursday said: "The document that was forwarded to the UCI by the RFEC only represents one element of the disciplinary proceedings undertaken by the Spanish Federation - and upon which the rider may express an opinion before being subject to the ruling - and cannot be used for the purpose of a potential appeal to the Court of Arbitration for Sport (Cas) in Lausanne."
Contador started his career under the guidance of fellow Spaniard Manolo Saiz, who was arrested in 2006 in the Operation Puerto blood-doping scandal.
In 2007, Contador joined the Discovery Channel team, taking his maiden Tour title under Johan Bruyneel, who masterminded Lance Armstrong's record seven triumphs.
That year Contador was grilled about his possible involvement in the Puerto affair, but the Spanish cyclist was never formally charged and has has strongly denied any involvement in the scandal.
In 2008, he could not defend his Tour title after former team Astana were banned from the race because of their past doping record.
However, he did win the Giro and the Vuelta to become only the fifth rider to win in all three Grand Tours.
Any ban would leave Contador's new team, Saxo Bank, without a leader for the 2011 Tour.
Contador is the latest in a string of high-profile doping cases, including 1996 Tour winner Bjarne Riis and Landis, to have rocked cycling.
Armstrong is at the centre of a federal investigation in the United States after Landis alleged in 2010 the 39-year-old Texan and other prominent figures in the sport had breached doping regulations.
Seven-time Tour winner Armstrong has always denied doping.