A leading pentathlete, ranked 19th in the world and who represented Lithuania at the 2008 Beijing Olympics but received Russian citizenship in 2011 after marrying a Russian, has been blocked from competing at London 2012.
Double World Cup winner Donata Rimsaite may now take her case to the Court of Arbitration for Sport.
Lithuania's National Olympic Committee voted in January to bar Rimsaite from London 2012, under a provision that allows a country's sporting authorities to veto Olympic participation within three years of an athlete switching allegiance.
Russian authorities are ready to take the case to the Court of Arbitration for Sport in Swizterland, but are hoping it will first be resolved by the International Olympic Committee, said Vyacheslav Aminov, president of the Russian Modern Pentathlon Federation.
"A legal application to the court to change the Lithuanian Olympic Committee's decision has already been prepared by Swiss lawyers, but whether it will be submitted depends on whether the IOC executive committee will consider the matter in May," he said.
"If we understand that this will happen, then Rimsaite won't go to court. If we understand that the IOC won't look at the case, then Rimsaite will take legal action," he said.
Rimsaite's cause has attracted support from IOC members, Aminov claimed.
"Many members of the executive committee have come out in our favour.
Some Lithuanian media outlets have cast doubt on Rimsaite's version of events after she told Lithuania's TV3 channel that she was receiving far higher funding after switching to Russia.
Lithuanian newspaper Lietuvos Rytas reported that there was no record of Rimsaite's husband's existance in Russia.
Rimsaite appeared in person to address the Lithuanian Olympic Committee before the crucial vote, which she lost 49-1 with seven abstentions.
The head of the Lithuanian Modern Pentathlon Federation had threatened to resign unless she was banned from London 2012.
Rimsaite won the 2008 and 2009 World Cup finals, but last won an event in Italy in April 2011, and was ranked 19th in the world when the International Modern Pentathlon Union published the latest ratings.