Lawyers for President Donald Trump’s former campaign chairman Paul Manafort will try to convince a U.S. judge on Friday their client did not breach his plea agreement with Special Counsel Robert Mueller in a hearing that could lead to a longer prison sentence.

Mueller’s office in November accused Manafort of violating his agreement to cooperate with the special counsel’s investigation into Russia’s role in the 2016 U.S. presidential election.

The special counsel said Manafort, 69, repeatedly lied to federal investigators on at least five different subjects ranging from his contacts with Trump administration officials in 2018 to his interactions with his former business partner in Ukraine Konstantin Kilimnik, who Mueller’s office has said has

ties to Russian intelligence.

The hearing gives Manafort’s attorneys a chance to persuade U.S. District Judge Amy Berman Jackson that the veteran political consultant, who earned millions of dollars in work for Ukraine’s former pro-Russia president, did not breach the plea arrangement. If Jackson finds he did, Manafort could face a much steeper prison term.

Manafort’s attorneys in a court filing on Wednesday said he had difficulty recalling “certain facts and events,” but did not intentionally provide false information to the special counsel.

Jackson ordered Manafort to attend the high-stakes hearing, denying his request to skip it, but ruled he can wear a suit, rather than a prison uniform.

Some of the details about Mueller’s accusations about Manafort’s lying were made public inadvertently by his defense lawyers in a Jan. 8 court filing.

Prosecutors said Manafort lied about sharing election polling data with Kilimnik, about his discussions with Kilimnik concerning a “Ukrainian peace plan”

and about a meeting the two had in Madrid.

Kilimnik, who has denied ties to Russian intelligence, was indicted by Mueller in June 2018 on obstruction of justice charges.

Manafort pleaded guilty in September 2018 in a federal court in Washington to attempted witness tapering and conspiring against the United States, a charge covering conduct including money laundering and unregistered lobbying. He was convicted separately by a jury in Alexandria, Virginia in August 2018 of

bank and tax fraud in a parallel case also brought by Mueller.

The Virginia case alone could bring Manafort up to 10 years in prison for the eight guilty counts, according to sentencing experts. Sentencing in that case is scheduled for Feb. 8.

Mueller, a former FBI director, is investigating whether Trump’s campaign conspired with Moscow and whether the president unlawfully sought to obstruct the probe. Russia has denied election interference. Trump has denied collusion with Moscow.