Lausanne - Spanish cyclist Alberto Contador will on Monday fight a bid by cycling's governing body to impose a doping ban which could strip him of his 2010 Tour de France win.
The three-time Tour de France champion is to plead his case at the Lausanne-based Court of Arbitration for Sports, which has been charged with examining if minute traces of clenbuterol found in a urine sample in 2010 is proof that Contador used drugs to enhance his performance.
The Spanish Cycling Federation (RFEC) initially cleared Contador of any wrongdoing after he claimed his sample had been contaminated by a steak which he ate on the second rest day of the 2010 Tour de France.
That ruling allowed Contador to continue competing, but the International Cycling Union (UCI) and the World Anti-Doping Agency (WADA) filed appeals to CAS.
The four-day hearing at CAS will take place behind closed doors and the court has said that it will "issue its decision with reasons as soon as possible but probably not sooner than several weeks following the completion of the hearing".
At the heart of the case is the 50 picograms of clenbuterol, found in his urine on 21 July 2010, during a rest day of the Tour de France at Pau.
Although known as a powerful drug used to treat asthma, clenbuterol can also help build up lean muscle mass and burn off fat.
Contador's lawyers argue that he was contaminated by a steak consumed the previous evening and which originated from his native Spain.
His defence will say that even if the anabolic agent used to boost cattle growth has been banned in the European Union, there remains the possibility that it is still being used by some.
The Spanish Cycling Federation bought the argument and in February cleared Contador of all charges.
In Spain, where Contador has the support of personalities including outgoing prime minister Jose Luis Zapatero, only beef producers found the argument of bad taste.
However, the UCI and WADA were not convinced and decided to file an appeal at sport's highest court - CAS.
CAS had planned to rule before the 2011 edition of the Tour, but in June, the hearing was pushed to August on Contador's request.
Later, WADA sought a further extension after Contador's lawyers sent them 3 000 pages of documents shortly before their scheduled meeting in Lausanne.
WADA and UCI have so far remained tightlipped about the evidence that they would be putting before the CAS.
Some media outlets have raised the possibility that the cyclist may have had a banned blood transfusion, shown by a high concentration of plastic residues measured in his urine at the same time as the clenbuterol.
If CAS upholds appeals by the UCI and the WADA, the Spaniard faces a competition ban and being stripped of his 2010 Tour de France title and the Giro d'Italia, which he won for a second time this year, and any other victories since July 2010.
Contador meanwhile insists that he has never taken banned drugs, even going as far as to pass a lie detector test to prove his innocence.