Mueller persuaded Gates to cooperate with him on the probe as part of a plea deal - dialing up the legal pressure on Manafort, who has not opted to help investigators. Several charges against Gates were dropped on Tuesday.

While in court on Wednesday, Manafort was scolded by Jackson for publicly maintaining his own innocence after Gates’ plea - something that she said could prejudice a jury.

“I can certainly understand the impulse to not let that go by without asserting your innocence,” Jackson told Manafort. But it can’t happen again, she said, or she could hold him in contempt.

On October 30, Manafort, 68, pleaded not guilty with Gates in the first disclosed charges in Mueller’s investigation of alleged Russian interference in the 2016 US presidential election. 

The men were originally accused in a 12-count indictment of conspiring to defraud the United States since 2006 by hiding tens of millions of dollars from their work for a Russia-friendly political party in Ukraine and former president Viktor Yanukovich.

On Friday, Gates, 45, pleaded guilty to reduced charges in exchange for cooperating with prosecutors. He is the third former Trump aide to publicly admit guilt in Mueller’s probe.

In conjunction with Gates’s plea deal, Mueller’s team added tax evasion and bank fraud charges against Manafort.

He already faced counts alleging conspiracy to launder more than US$30 million, making false statements, failing to follow lobbying disclosure laws and working as an unregistered foreign agent. 

Manafort has a home in Virginia and the counts of lying on tax returns and conspiring to commit bank fraud were filed there because of a technical requirement that, as a defendant, he appear in federal court in the state in which he filed tax returns.

A court filing indicated prosecutors initially sought to combine the new charges with the pre-existing indictment in federal court in Washington.

But Manafort would have had to agree – and he declined to, leading to the possibility of separate trials in neighbouring jurisdictions.

This week’s arraignments were scheduled after, Jackson a Washington judge, granted Manafort permission to travel to Long Island to attend the wake and funeral of his father-in-law, who died Saturday, and to return Tuesday to his Alexandria residence, where he remains in home confinement.

Manafort is still under house arrest after Jackson last week rejected his bid to revise a previously approved US$10 million bail deal by swapping out the properties he would use as security for bail.

Prosecutors opposed Manafort’s request, alleging he was involved in additional bank fraud conspiracies in which they contend Manafort inflated his income to get a US$9.5 million loan secured by property he falsely said was mortgage-free. 

Manafort asserted his innocence of all counts in a statement through spokesman Jason Maloni last week. 

“The new allegations against Mr Manafort, once again, have nothing to do with Russia and 2016 election interference/collusion,” the statement said. 

“Mr Manafort is confident that he will be acquitted and violations of his constitutional rights will be remedied.”

Also before Jackson is Manafort’s lawsuit challenging his indictment and Mueller’s appointment as special counsel, arguing Deputy Attorney General Rod J Rosenstein and Mueller have exceeded their authority in charging him. 

The Justice Department has asked Jackson to toss out the case, saying the proper forum for dismissing charges is his criminal case.

It has also emerged on Wednesday that some of the charges against Gates were dropped on Tuesday.

A court filing showed that prosecutors working for Robert Mueller dropped the charges just days after he was indicted for participating in a conspiracy to hide millions of dollars in fees he was paid for lobbying work and evade US taxes.

This report includes information from Associated Press, The Guardian, Reuters and The Washington Post.