Special counsel Robert Mueller submitted a court filing Monday alleging that former Donald Trump campaign chairman Paul Manafort breached his plea deal by lying during his interviews with prosecutors.

Manaforts lies, which are not specified in the document, nullify all the promises federal prosecutors made to him as part of the plea agreement he reached two months ago in the investigation over Russian meddling in the 2016 presidential election, Muellers filing argues.

A breach relieves the government of any obligations it has under the agreement, including its agreement to a reduction in the Sentencing Guidelines for acceptance of responsibility, but leaves intact all the obligations of the defendant as well as his guilty pleas, the filing reads.

Lawyers for Manafort, who pleaded guilty to conspiracy against the United States and conspiracy to obstruct justice as part of his plea deal in September, say the filing is invalid. He was also convicted on eight counts of financial fraud in August in connection with his work as a political consultant in Ukraine.

Manaforts plea deal with Mueller marked a major development in the special counsels investigation into Donald Trump s 2016 presidential campaign. By agreeing to cooperate with Mueller, Manafort was expected to provide the investigation with valuable information about what, if any, role Trumps campaign had in Russias interference in the election.

His decision to cooperate with the investigation all but guaranteed he could not count on a presidential pardon from Trump.