The U.S. Department of Justice announced Friday that it has joined a civil fraud lawsuit against disgraced cyclist Lance Armstrong.  The suit alleges that Armstrong violated their sponsorship agreement by using performance-enhancing drugs while the U.S. Postal Service served as team sponsor from 1996 to 2004, during which Armstrong won six of his seven Tour De France titles. 

The suit was originally filed under seal by former cyclist and confessed doper Floyd Landis in 2010.  It names Armstrong, his team manager Johan Bruyneel, and Tailwind Sports, the team's management company, as defendants.  From 2001 to 2004, the Postal Service paid $31 million in sponsorship fees.  Under the Federal False Claims Act, the government can recover up to three times that amount in damages -- over $90 million -- and as the main whistleblower, Landis can get up to 25 percent.

SEE ALSO: Opinion | Lance Armstrong Doesn't Owe Us Anything

Ronald C. Machen Jr., U.S. Attorney for the District of Columbia, told CNN that the Postal Service's sponsorship of Armstrong during his most successful years has now been "unfairly associated" with the systemic doping program he allegedly helped create and manage with government money. 

"In today's economic climate, the U.S. Postal Service is simply not in a position to allow Lance Armstrong or any of the other defendants to walk away with the tens of millions of dollars they illegitimately procured," he said.

Robert Luskin, an attorney for Armstrong, said in a statement that negotiations between Armstrong and federal lawyers broke down over disagreements on how the Postal Service was affected by the sponsorship.

"The Postal Service's own studies show that the service benefited tremendously from its sponsorship -- benefits totaling more than $100 million," he said. 

SEE ALSO: Armstrong Apologizes To Livestrong Foundation

The Justice Department's decision only adds to the already numerous problems facing Armstrong.  In addition to the federal lawsuit, he also faces one from Texas insurance firm SCA promotions, who is seeking $12 million for bonus money paid to Armstrong for his Tour De France victories, which were stripped from him by cycling's international governing body UCI this past October. 

Armstrong also announced this past Wednesday that he would not assist the USADA in their probe into doping in cycling, meaning that his chances of having his lifetime ban from World Anti-Doping Agency-sanctioned sports reduced are now unlikely. 

The government will file its formal complaint within the next two months.

Reach Jeremy HERE or follow him on Twitter