The United States Government has filed court papers accusing disgraced cyclist Lance Armstrong of defrauding the US Postal Service out of millions of dollars of sponsorship money, according to reports.

The US Department of Justice indicated in February it would join the whistleblower lawsuit brought in 2010 by Armstrong's former team-mate Floyd Landis.

It is said to have filed a formal complaint ahead of Tuesday's deadline, alleging the American and others violated their contract and defrauded the US Postal Service by failing to adhere to cycling's doping regulations while receiving sponsorship money.

The lawsuit also names former team director Johan Bruyneel and team management company Tailwind Sports among the defendants.

Armstrong was stripped of his seven Tour de France titles and handed a life ban from cycling last year after the United States Anti-Doping Agency produced a damning portfolio of evidence that he had doped during his run of success.

The 41-year-old later confessed he had cheated during an interview with television host Oprah Winfrey.

Six of Armstrong's wins on the Tour de France came while his team were sponsored by the US Postal Service (USPS).

The USPS sponsorship was from 1999 to 2004, with $31 million paid between 2001 and 2004 alone, the Department of Justice said in February.

The US government is reportedly suing Armstrong under the False Claims Act, and wants to be reimbursed for three times the damages, plus penalties.

Having made the original allegations, Landis would potentially receive a considerable share of any money recovered.