Contador is not taking part in the Paris-Nice race starting on Sunday
Cycling's governing body has until 24 March to appeal against the overturning of Alberto Contador's one-year doping ban by the Spanish federation.
The 28-year-old three-time Tour de France champion tested positive for banned substance clenbuterol during the 2010 race.
But the Spanish cycling federation accepted his claim that contaminated meat had caused the failed test.
The UCI is considering an appeal to the Court of Arbitration for Sport (Cas).
Pat McQuaid, the International Cycling Union president, said: "Our principal lawyer...will start working on the Contador case on Monday.
"I can't give an opinion on whether he is guilty or not. But the Contador case is difficult for the sport. It's like a cloud over our head."
The World Anti-Doping Agency (Wada) is also considering an appeal against the Spanish federation's decision and has until 24 April to do so.
Contador has always maintained his innocence and insisted he has never taken performance-enhancing drugs and said he was a "victim" when the muscle-building and fat-burning drug clenbuterol was discovered in his system.
But the Royal Spanish Cycling Federation (RFEC), which had imposed the 12-month punishment, subsequently cleared him of knowingly using a banned drug last month.
Contador is not competing in the week-long Paris-Nice race, the first big event of the year, which starts on Sunday.