However, the deal could involve Manafort's cooperation with Mr Mueller's investigation into possible collusion between the Trump campaign and Russian Federation.
He was convicted last month in a separate federal trial in Alexandria, Va., on eight charges of bank and tax fraud, also related to his work in Ukraine.
The case was brought by Mueller's team, which is probing potential crimes related to the 2016 election.
Manafort, 69, was a key figure in Mr Trump's inner circle, but the president has since sought to distance himself from his former adviser.
EU parliament pushes Hungary sanctions over Orban laws - International
The most severe punishment under the Article 7 procedure is stripping Hungary of its voting rights in the EU. Should the EPP move against it, Fidesz would be under huge pressure to leave the group.
In addition to the witness tampering counts, Manafort had been formally charged with acting as an unregistered foreign agent, conspiring to launder money and lying to the Federal Bureau of Investigation and Justice Department about the nature of his work. Jury selection was due to start on Monday.
Prosecutors, who made a point of noting the activity occurred "at least through 2016", used bank records and other documents to show what they say Manafort did to hide evidence of his work for Ukrainian politicians, hide millions in proceeds in offshore accounts, and then spend the money lavishly on clothing, luxury items, homes and cars.
That posture drew plaudits from Trump, who praised his former campaign chairman for his unwillingness to cooperate with the special counsel. A mistrial was declared on the remaining 10 charges after jurors could not reach a unanimous verdict.
Earlier this year, Manafort derided Gates, his former business partner, for striking a deal with prosecutors that provided him leniency in exchange for testimony against his former partner. The money, the newspaper reported, came from the pro-Russian party of Viktor Yanukovych, the onetime Ukraine president. But Manafort has not been charged with anything related to the campaign. Manafort would be the fifth Trump aide to plead guilty in connection to the special counsel's probe.
Manafort has been in jail since June, when the judge in the D.C. case, U.S. District Judge Amy Berman Jackson, threw him in pretrial detention for alleged witness tampering.