Prosecutors allege that a Russian partner of Manafort's, Konstantin Kilimnik, helped him try to persuade witnesses to lie to the jury when Manafort's case comes to trial in Washington, D.C., this autumn.
Mr Manafort is also charged with money laundering, illegal foreign lobbying, and lying to federal officials.
The new charges are related to the accusation that Manafort hired a firm of former European officials to illegally lobby in the US on issues related to Ukraine.
In the days that followed and through April, Manafort and Kilimnik suggested the two witnesses who worked on the Hapsburg group project say the group focused on Europe and "never lobbied in the United States", according to an encrypted message between Kilimnik and one witness that prosecutors obtained.
Kilimnik is a longtime associate of Manafort.
Prosecutors say the "P" in the message refers to Manafort, and that the assertions in the texts are untrue.
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Manafort already faces lengthy indictments in both Washington, D.C., and Virginia on charges related to tax fraud and other financial crimes.
The Hapsburg group's work is one of several operations prosecutors say Manafort directed as part of a covert lobbying campaign on behalf of Ukraine, its then-president, Viktor Yanukovych, and the pro-Russian Party of Regions.
In court papers, the Federal Bureau of Investigation is alleging that at least one witness in the Manafort case was contacted by the former Trump aide and coached on what he should say about his lobbying practices.
"Mr. Manafort is innocent and nothing about this latest allegation changes our defense", Manafort spokesperson Jason Maloni told ABC News in a statement on Tuesday.
Manafort's lawyers were expected to respond to those claims Friday.
Over in the District of Columbia, Judge Amy Berman Jackson will hold a hearing in Manafort's case on June 15, when she will rule on the prosecutors' motion to revoke Manafort's bail, and jail him until the start of the trial. He also has denied being connected to Russian intelligence agencies. Kilimnik later took on more responsibilities, serving as Manafort's liaison to Oleg Deripaska, a Russian billionaire who paid Manafort to advise him on investments.
Earlier on Friday, Mr Trump denied that he was considering pardoning Mr Manafort.
Spencer S. Hsu is an investigative reporter, two-time Pulitzer finalist and national Emmy Award nominee.