WASHINGTON – A federal judge concluded on Wednesday that Paul Manafort had lied repeatedly to federal prosecutors after having promised to cooperate in their investigation of Russian interference in the 2016 election.

The decision upends an agreement that Manafort, President Donald Trump's former campaign chairman, had struck with prosecutors before pleading guilty to charges of conspiracy and obstruction of justice. It means Manafort faces the prospect of a longer prison sentence.

U.S. District Judge Amy Berman Jackson said in an order Wednesday that Manafort "intentionally made false statements" to the FBI and to prosecutors about his interactions with a Russian associate and other subjects.

Manafort pleaded guilty in September to two charges in special counsel Robert Mueller's investigation. His agreement with prosecutors called for him to cooperate with their investigation in exchange for the possibility of a reduced sentence.

Mueller sought to void the plea agreement in November after prosecutors alleged that Manafort had misled them about his interactions with a Russian business associate, his contacts with Trump's administration and other subjects. Manafort's lawyers mistakenly revealed that one of the lies he was accused of telling related to his sending polling data to a Russian associate during Trump's campaign.

Manafort's lawyers told Jackson that he did not intend to mislead to investigators, but may have forgotten the details of events during a hectic presidential campaign.

"Mr. Manafort did not lie," his lawyers said in a filing Wednesday.

Prosecutors had accused Manafort of lying to them about five subjects, ranging from his interactions with a Russian business associate to his contacts with the Trump administration.

Jackson ruled on Wednesday that Manafort had intentionally misled investigators about three of the five subjects. She ruled prosecutors had not shown that Manafort's misstatements to them about his contacts with people in the Trump administration were intentional.

But Jackson said she was persuaded that Manafrot had provided false information to the special counsel, violating his plea agreement. That means Mueller's office is no longer bound by the deal that would have required prosecutors to seek a reduced sentence.

During closed hearings about whether he breached the plea agreement for a shorter prison term, prosecutors alleged that Manafort lied about how many times he met with his co-defendant in the case, a Russian national, Konstantin Kilimnik, according to a partially redacted transcript of a hearing Feb. 4. Prosecutors contend Kilimnik has ties to Russian intelligence, which he has denied.

One of the meetings was Aug. 2, 2016, when Manafort met Kilimnik at the Grand Havana Room, a private club in a building then owned by Kushner Companies, including Trump’s son-in-law Jared Kushner.

“This goes, I think, very much to the heart of what the special counsel’s office is investigating,” Andrew Weissmann, one of Mueller’s prosecutors, told Jackson at the Feb. 4 hearing.

The meeting came two weeks after the Republican convention, which Weissmann said was “an unusual time for somebody who is the campaign chairman to be spending time, and to be doing it in person.” Weissmann said Manafort, his deputy Rick Gates and Kilimnik “took the precaution” of leaving the meeting by different doors.

Manafort’s lawyer, Richard Westling, said the campaign chairman forgot about the meeting rather than trying to hide it. Manafort quit Trump’s campaign Aug. 19, 2016, after revelations about his work in Ukraine, but Westling said he continued his relationship with Kilimnik.

“He told the government all along he remained open to opportunities over there,” Westling said of Manafort.

Westling said Manafort shared documents at the meeting that were difficult for the unfamiliar to understand. Westling called the information “gibberish” and said “it’s not easily understandable.”

Manafort met with prosecutors and FBI agents on 12 occasions, including three before entering the plea agreement. He also testified before a grand jury on Oct. 26 and Nov. 2. Prosecutors informed Manafort's lawyers on Nov. 8 that they "believed that Manafort had lied in multiple ways and on multiple occasions."

Manafort’s guilty plea, along with a Virginia jury conviction in August, were for crimes related to his work with a pro-Russia faction in Ukraine. Sentencing for both cases has been postponed, awaiting the outcome of Jackson's decision about whether Manafort breached his plea agreement.