Lance Armstrong is being sued by the US government. Armstrong is accused of defrauding the US Postal Service by taking millions of dollars in sponsorship money while breaking professional cycling rules by doping. On Tuesday, the US government filed court documents against the cyclist, laying out their case against Armstrong.

Lance Armstrong is being sued under the False Claims Act and the suit is asking to recoup up to three times the amount it lost as a result of the fraud, which may bring in over $100 million. The complaint that was filed also alleges breach of contract, fraud, and unjust enrichment. The Department of Justice first indicated in February that it would join lawsuits initially started in 2010 by Floyd Landis, whistleblower and Armstrong's former teammate.

Armstrong's lawyers have labeled the suit as opportunistic. Attorney Elliot Peters said in a statement, "The US Postal Service benefited tremendously from its sponsorship of the cycling team. The USPS was never the victim of fraud. Lance Armstrong rode his heart out for the USPS team, and gave the brand tremendous exposure during the sponsorship years."

Between 1998 and 2004, Armstrong and his team-mates were paid $40m by the US Postal Service. Armstrong's salary during that time, excluding bonuses, was $17.9m, according to the suit. Allegations that Armstrong was doping were swirling for years, and in January 2012, he confessed to Oprah Winfrey that they were true. He has since been stripped of his seven Tour de France titles and banned for life from cycling. The suit accuses Armstrong of using at least one banned substance in connection with every Tour de France between 1999 and 2005. "Moreover, he knew that his team-mates were engaged in similar doping practices, and he actively encouraged and facilitated those practices," the complaint said.

A lawyer for Landis, Paul Scott, said in a statement that he was "pleased to see the US take this important step toward recovering taxpayer dollars lost to fraud".