Prosecutors with special counsel Robert S. Mueller III said Monday that Paul Manafort breached his plea agreement, accusing President Trump’s former campaign chairman of lying repeatedly to them in their investigation into Russian interference in the 2016 election.

Manafort denied doing so intentionally, but both sides agreed in a court filing that U.S. District Judge Amy Berman Jackson of the District should set sentencing immediately.

The apparent collapse of Manafort’s cooperation agreement is the latest stunning turnaround in his case, exposing the longtime Republican consultant to at least a decade behind bars after he pleaded guilty in September to charges of cheating the Internal Revenue Service, violating foreign-lobbying laws and attempting to obstruct justice.

The filing also indicated that Mueller’s team may have lost its potentially most valuable witness in Manafort, a top campaign official present at discussions at the heart of the special counsel’s mission to determine if any Americans conspired with Russia’s efforts to sway the U.S. election.

Still, prosecutors may know more about Manafort’s interactions than he realized, allowing them to catch him in alleged lies.

Separately Monday, conservative author Jerome Corsi, who has ties to a longtime Trump adviser, said he rejected a deal offered by Mueller to plead guilty to one count of perjury because, he said, he did not intentionally lie to investigators.


Paul Manafort (Alexandria Sheriff's Office)

It was not clear what the men already have told investigators or whether their lack of cooperation would mark a significant setback for Mueller’s investigation.

As part of his plea agreement, Manafort promised to tell the government about “his participation in and knowledge of all criminal activities.” Prosecutors did not elaborate on areas where they contend Manafort lied or what evidence led them to that conclusion. A Mueller spokesman declined to comment.

“After signing the plea agreement, Manafort committed federal crimes by lying to the Federal Bureau of Investigation and the Special Counsel’s Office on a variety of subject matters, which constitute breaches of the agreement,” prosecutors wrote. “The government will file a detailed sentencing submission to the Probation Department and the Court in advance of sentencing that sets forth the nature of the defendant’s crimes and lies.”

Manafort disputes that characterization. His attorneys write in the joint filing that he “has provided information to the government in an effort to live up to his cooperation obligations.”

A Manafort spokesman did not immediately respond to a request for comment.

Manafort pleaded guilty Sept. 14, on the eve of jury selection for his trial in Washington, to two charges — conspiring to defraud the United States and conspiring to obstruct justice — admitting to years of financial crimes related to his undisclosed lobbying work for a pro-Russian political party and politician in Ukraine.

Under the agreement with prosecutors, Manafort faced a maximum prison sentence of 10 years in the District case, not counting a sentence for his August conviction in Virginia for bank and tax fraud.

The longtime lobbyist also was ordered to forfeit an estimated $15 million he hid from the IRS but was permitted to keep some property held with relatives.

In return for his cooperation, he hoped to have prosecutors recommend leniency, possibly slicing years off his term of incarceration.

If he is found to have breached the deal, he would lose any sentencing credits for acceptance of responsibility, prosecutors said. Evidence of other crimes could also subject Manafort to an increase in the seven-to-10-year sentence he faces in Virginia. He is set to come before U.S. District Judge T.S. Ellis III of Alexandria for sentencing in February.

Before his plea, Manafort vigorously fought the charges. His defenders had long insisted that he would not cooperate with Mueller and that he did not have information that would incriminate the president.

But in plea papers, Manafort agreed to cooperate “fully and truthfully” with the investigation by the Office of Special Counsel, including participating in interviews and debriefings, producing any documents in his control, testifying, and agreeing to delay sentencing until a time set by the government.

Monday’s filing came after Manafort talked in detail to prosecutors before his plea, and despite numerous visits by him and his lawyers since to prosecutors’ offices.

Kevin Downing, an attorney for Manafort, said at the time of the plea that it included a full cooperation agreement. “He wanted to make sure his family remained safe and live a good life,” Downing said outside the courthouse. “He has accepted responsibility.”

Matt Zapotosky and Rosalind S. Helderman contributed to this report.