Federal prosecutors accused former Trump presidential campaign chairman Paul Manafort of witness tampering in his criminal case. Picture: AP Photo/Jose Luis Magana

Washington - Federal prosecutors accused former Trump presidential campaign chairman Paul Manafort of witness tampering late Monday in his criminal case and asked a federal judge to consider revoking or revising his release.

Prosecutors accused Manafort and a longtime associate they linked to Russian intelligence of repeatedly contacting two members of a public relations firm and asking them to falsely testify about secret lobbying they did at Manafort's behest.

The firm of former senior European officials, informally called the "Hapsburg group," was secretly retained in 2012 by Manafort to advocate for Ukraine, where Manafort had clients, prosecutors charged.

In court documents, prosecutors with Special Counsel Robert Mueller allege that Manafort and his associate - referred to only as Person A - tried to contact the two witnesses by phone and through an encrypted messaging programme. The description of Person A matches his longtime business colleague in Ukraine, Konstantin Kilimnik.

Manafort, 69, has been on home confinement pending trial.

FBI agent Brock Domin said that one of the public relations firm's executives identified as Person D1 told the government he "understood Manafort's outreach to be an effort to 'suborn perjury' " by encouraging others to lie to federal investigators by concealing the firm's work in the United States.

Spokesmen for Manafort and the special counsel's office, who are under a court gag order in the case, declined to comment.

Manafort has pleaded not guilty to conspiracy, money laundering, and tax and bank fraud charges related to his lobbying work for a pro-Russian political party in Ukraine and former Ukrainian president Viktor Yanukovych.

The filings mark the second time prosecutors have complained to the judge about Manafort's behavior awaiting trial. Early in the case, after he was released to his home, they investigators said they intercepted emails showing Manafort helped write an opinion piece defending his actions that ran in a Ukrainian publications.

Prosecutors filed the motion Monday in Manafort's pending Washington, D.C., case, which includes charges of filing misleading lobbying disclosure statements, and also noted his alleged tampering in his related tax and bank fraud case in Alexandria, Virginia.

If a judge were to revoke Manafort's bail conditions and order him to jail pending his two trials this summer, that would intensify the pressure on him to reach a plea deal with prosecutors.

Many white-collar prosecutions are built by charging people lower down in an organisation and then "flipping" those defendants into prosecution witnesses to get leniency in their sentencing. Manafort has repeatedly declared his intention to fight the charges against him, but it wasn't immediately clear Monday night whether the renewed prospect of going to jail would alter his legal strategy.

Manafort's potential value as a prosecution witness is unclear, but as Trump's former campaign chairman he participated in multiple high-level discussions within the campaign that are of great interest to investigators.

According to a February indictment, Manafort in 2012 and 2013 used offshore accounts to wire more than 2 million euros to pay the former politicians, who were described as independent actors instead of paid lobbyists.

Monday's court filing highlighted anew the role of "Person A," whom prosecutors did not name but described in detail in related cases. The description matches Kilimnik, the Russian manager of Manafort's lobbying office for 10 years in Ukraine.

A Russian citizen born in Ukraine, Kilimnik worked for Manafort in Kiev first as a translator and later as the in-country operator of Manafort's operations. He continued to serve as a close Manafort associate during the months Manafort worked for President Trump's campaign, including visiting Manafort in person in New York in May and August 2016.

He is a Russian army veteran who trained at a language school that experts say is recruiting ground for a Russian intelligence agency. Kilimnik has denied having intelligence ties.

Kilimnik did not respond to a request for comment Monday evening.

During his August 2016 meeting with Kilimnik, Manafort has said he and his longtime Kiev office manager discussed, among other topics, the ongoing campaign, including the hacking of Democratic National Committee emails. Stolen DNC emails had been released by WikiLeaks the previous month, and the hack was widely suspected to be the work of Russia.

During Kilimnik's time working for Manafort in Kiev, he had served as a liaison for Manafort to the Russian aluminum magnate Oleg Deripaska, with whom Manafort had done business. Emails previously described to The Post show that Manafort asked Kilimnik during the campaign to offer Deripaska "private briefings" about Trump's effort. A Deripaska spokeswoman has said the billionaire, a close ally of Russian President Vladimir Putin, was not offered and did not receive such briefings.

The Washington Post