The sentencing memo filed on Saturday by Mueller's office, which is investigating Russia's role in the 2016 US election and whether Trump's campaign conspired with Moscow, increases the likelihood that Manafort will spend the rest of his life behind bars.

Manafort pleaded guilty in a federal court in Washington last September to conspiracy against the United States - a charge that includes a range of conduct from money laundering to unregistered lobbying - and conspiracy to obstruct justice for his attempts to tamper with witnesses in his case.

The sentencing memo said Manafort committed crimes that cut to "the heart of the criminal justice system" and over the years deceived everyone from bookkeepers and banks to federal prosecutors and "members of the executive branch of the United States government".

He is due to be sentenced on March 13.

While Mueller did not recommend a specific sentence he portrayed Manafort as a "hardened" criminal who was at risk of repeating criminal behaviour once he is released from prison.

"For over a decade, Manafort repeatedly and brazenly violated the law," Mueller's office said in a sentencing memorandum released by the court.

"His criminal actions were bold, some of which were committed while under a spotlight due to his work as the campaign chairman and, later, while he was out on bail from this Court."

Manafort, a veteran Republican political consultant, who earned millions of dollars working for pro-Russian politicians in Ukraine, will turn 70 in April and faces a potentially lengthy sentence in a second case in Virginia in which he was convicted last year of financial crimes.

Australian Associated Press