(CNN) -- The U.S. Department of Justice has joined the whistle-blower lawsuit against cyclist Lance Armstrong that was originally filed by a former teammate, an attorney for Armstrong said Friday.
"Just a little while ago we got an email from the Department of Justice (DOJ) notifying us that DOJ is joining the case," attorney Mark Fabiani said in an e-mail to CNN.
Armstrong, the one-time legendary and now disgraced cyclist, has admitted to using performance-enhancing drugs.
The lawsuit accuses the former management of Armstrong's team of defrauding the federal government of millions of dollars because it knew about the drug use and didn't do anything.
The federal government had been evaluating for weeks whether to intervene in the lawsuit.
Another attorney for Armstrong, Robert Luskin, said that ongoing discussions between the federal government and Armstrong's legal team had collapsed.
"Lance and his representatives worked constructively over these last weeks with federal lawyers to resolve this case fairly, but those talks failed because we disagree about whether the Postal Service was damaged," Luskin said. "The Postal Service's own studies show that the Service benefited tremendously from its sponsorship -- benefits totaling more than $100 million."
Former teammate Floyd Landis, who was stripped of his 2006 Tour de France title after failing a drug test, filed the lawsuit in 2010 against the team, which was sponsored the U.S. Postal Service.
As of midday Friday, the whistle-blower suit remained under court seal.
The suit also names as defendants Johan Bruyneel, who had managed the U.S. Postal Service and Discovery racing teams on which Armstrong raced, and Tailwind Sports, which was the team's management entity, Fabiana said.
For years, Armstrong had denied drug use and blood doping, but he publicly admitted such use in January, three months after international cycling's governing body stripped him of his seven Tour de France titles.
That stripping came after a damning report by the U.S. Anti-Doping Agency accused Armstrong and his team of the "most sophisticated, professionalized and successful doping program" in cycling history.