A new court filing indicates there may be tension between Paul Manafort and his lawyers, former federal prosecutors tell The Daily Beast.

On Monday night, special counsel Robert Mueller’s team told a federal judge that Donald Trump’s former campaign chairman has repeatedly lied to them and “breached” their cooperation agreement. Manafort had agreed to work with Mueller after he was convicted on several counts in federal court in Virginia over the summer. Manafort then entered a plea deal with Mueller’s team before a second trial could start in Washington. In exchange for cooperation, Manafort’s team was hoping Mueller would recommend a lighter sentence for their client’s crimes. Instead, Mueller’s team now alleges he lied to them in the course of that cooperation and even “committed federal crimes.”

The response from Manafort’s legal team to these allegations raised eyebrows.

“After signing the plea agreement, Manafort met with the government on numerous occasions and answered the government’s questions,” the lawyers wrote. “Manafort has provided information to the government in an effort to live up to his cooperation obligations. He believes he has provided truthful information and does not agree with the government’s characterization or that he has breached the agreement.”

Mueller’s filing does not say what specific lies Manafort allegedly told, but Mueller’s office told the judge it will detail the nature of those alleged lies in the coming weeks. In response, Manafort’s lawyers will have the opportunity to defend their client.

Former prosecutors who spoke with The Daily Beast said they found the lawyers’ language surprising, particularly the statement that Manafort “believes” he told the truth. The language suggests Manafort’s own lawyers think he may have lied, they said. But it isn’t a consensus view.

A spokesperson for Manafort did not respond to requests for comment.

“ A defense attorney doesn’t know whether or not he actually has been truthful, but he can recount his statement that the client believes he’s been truthful. ” — Alan Dershowitz

“When they say the kind of thing they say in Paragraph 5 of that memo, ‘He did his best, he tried,’ they’re not asserting as his attorneys that he absolutely told the truth and was being done wrong by the Mueller team,” said Glenn Kirschner, who formerly headed the homicide unit for the D.C. U.S. Attorney’s office. “They are giving up their client right there.”

Lying to the FBI is illegal, and it’s a crime that has ensnared a host of Mueller’s targets: former national security advisor Michael Flynn, campaign advisor George Papadopoulos, campaign staffer Rick Gates, and Manafort-connected lawyer Alexander van der Zwaan.

Greg Brower, who was a senior official at the FBI and the U.S. attorney for Nevada, said he also thought Manafort’s attorneys’ statement may indicate they doubt their client’s honesty.

“I think that may in fact be right, that the lawyers by using that language are acknowledging that the objective facts would appear to suggest that their client is not telling the truth, but nevertheless that their client maintains that he is telling the truth,” he said.

Others disagree. Elie Honig, who prosecuted members of the Gambino crime family as an assistant U.S. attorney in the Southern District of New York, advised against reading too much into Manafort’s lawyers’ language.

“They’re basically saying, ‘Hey, Mueller thinks my guy is lying, we don’t think he is, and we think that we’ll be able to prove that he’s not lying,” he said. “They’re setting the stage for potentially a somewhat detailed, somewhat substantive evidentiary hearing over whether or not Manafort lied.”

Alan Dershowitz, a prominent criminal defense attorney, shared Honig’s view that the statement from Manafort’s lawyers doesn’t necessarily indicate they doubt their client’s truthfulness.

“That’s the best a defense attorney can do,” he said. “A defense attorney doesn’t know whether or not he actually has been truthful, but he can recount his statement that the client believes he’s been truthful.”

Sol Wisenberg, a former federal prosecutor who worked on Independent Counsel Kenneth Starr’s investigation of President Bill Clinton, said this reading of the filing is plausible.

“You would expect them to be a little more bold and say, ‘This is untrue, he has cooperated,’” said Wisenberg, who represents white-collar defendants.

Either way, it appears Manafort’s lawyers acknowledge he’s in trouble.

Robert Litt, former general counsel to the Office of the Director of National Intelligence, said the statement indicates Manafort’s lawyers are looking to push back against any forthcoming evidence he lied.

“It seems they know that their client has told Mueller things that objective evidence contradicts and that they are pinning their argument not on the accuracy of what he said but on his intent,” he said.