According to a motion filed by Special Counsel Robert Mueller's office, Manafort contacted witnesses by phone and an encrypted text messaging app in an attempt to secure "materially false testimony". In earlier filings, Person A has referred to Konstantin Kilimnik, a longtime Manafort associate who prosecutors have said has ties to Russian intelligence.
Prosecutors asked that the judge overseeing his case "revoke or revise" the order releasing him ahead of trial.
The government has not charged Manafort with the crime of witness-tampering or obstruction of justice.
Manafort's allegedly illegal contacts with the two people happened in the days after prosecutors unveiled a new set of criminal charges against him in DC related to his lobbying work.
The FBI has documents and statements from the two people, as well as telephone records and documents recovered through a search of Manafort's iCloud account showing that Trump's former campaign manager attempted communication while he was out on bail, according to Domin.
Mr Manafort, 69, denies charges which include fraud.More news: Concessions will not be implemented if United States imposes trade sanctions, warns China
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At one point, Manafort sent an encrypted text message to one of the witnesses, saying "This is Paul" and that "We should talk", the court filing alleges. I think, however, they were doing a number on Trump himself.
Despite the various indictments, Manafort has been out on bail and under house arrest, because he's being treated as a wealthy white man instead of a poor minority.
The former campaign chairman has been charged with money laundering, foreign lobbying violations, conspiracy against the US, and tax fraud, as well as other financial crimes. Manafort then tried sending hints via an app, sending headlines and reports to the witness such as a Business Insider article entitled, "Former European leaders struggle to explain themselves after Mueller claims Paul Manafort paid them to lobby for Ukraine".
"He had long-standing ties to Russia-backed politicians", DOJ attorney Michael Dreeben said about Manafort during a hearing connected to special counsel Robert Mueller's Russian Federation investigation.
Among those indicted are several former Trump campaign and administration staff, including Mr Manafort; Michael Flynn, the president's former national security adviser; Rick Gates, the former Trump deputy campaign chair; and George Papadopoulos, a foreign policy adviser to the campaign.