WASHINGTON » Lawyers for Lance Armstrong say the Justice Department has joined a lawsuit against the cyclist. The lawsuit alleges the former Tour de France champion concealed his use of performance-enhancing drugs for over a decade and defrauded his long-time sponsor, the U.S. Postal Service.

The suit the Justice Department is joining was filed in 2010 by former teammate Floyd Landis, who was stripped of his 2006 Tour de France title for doping.

An Armstrong lawyer, Robert Luskin, said today that negotiations with the government failed because “we disagree about whether the postal service was damaged.”

Said Luskin: “The postal service’s own studies show that the service benefited tremendously from its sponsorship — benefits totaling more than $100 million.”

The Landis lawsuit was filed under seal, but it will be unsealed now.