Donald Trump's former campaign chairman Paul Manafort lied to the special counsel investigating Russia's interference in the 2016 US presidential election, breaching his plea agreement, according to a court filing on Monday.
In return, prosecutors agreed not to bring additional charges against him and to ask a judge for a reduction of his sentence if he provided "substantial assistance".
In the latest filing, Mueller's team said Manafort "committed federal crimes" by lying about "a variety of subject matters" even after he agreed to truthfully cooperate with the investigation.
Manafort pleaded guilty to conspiracy and witness tampering on September 14, nearly a year after he was first charged and following his conviction by a jury in a separate but related case on eight tax and banking crimes.
As part of his plea deal, Manafort admitted to committing a host of money laundering and foreign lobbying crimes and fraud, giving the federal prosecutors leverage over him.
The 69-year-old Manafort was found guilty of eight counts of financial fraud after a federal trial in August in Virginia.
He pleaded guilty in October 2017 and pledged to cooperate with the Mueller probe, and was later sentenced after expressing his remorse that he "lied in an investigation that was important to national security".
With the end of the midterm elections, speculation mounted that Manafort might deliver information that could lead to charges against others in Trump's inner circle. The white house has continued to highlight the fact that the indictment has nothing to do with Trump himself.More news: Infighting and Regulatory Pressure Pushing Crypto Market Back to 2017
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By staying in touch with Trump's team while cooperating, experts say Manafort could be trying to keep all his options open, including angling for a potential presidential pardon.
Judge Randolph Moss reminded Papadopoulos that he had already waived his right to an appeal and that two other judges had upheld the legality of the Mueller appointment.
Trump's lawyers have also previously said that Manafort's legal team was keeping them informed of the former Trump campaign chairman's actions.
The rupture in relations could hamper Mueller's ability to turn an insider against Trump in the investigation of Russian meddling in the 2016 election, and has raised questions about whether Manafort could be angling for a presidential pardon.
The server reference relates to the Democratic National Committee, whose emails were hacked in a cyberattack believed to be an attempt by Russian Federation to influence the outcome of the 2016 election. A spokesman for Mueller, who was Federal Bureau of Investigation director at the time, said there was no dispute when Mueller left the club.
The defendant's lawyers insist he gave information he believed to be truthful.
The filing says Manafort does not agree with prosecutors' assertion that he has lied. In addition, prosecutors have said he could face as much as 10 years in prison for his conviction on tax evasion-related charges this summer.