After suggesting on Wednesday that their potential star witness, Mr Manafort's former associate Rick Gates, may not take the stand, the prosecution have also clarified they do intend to call him.

“We have every intention of calling him as a witness,” Greg Andres, a member of Mr Mueller's team said in a federal court in Alexandria, Virginia, outside Washington.

Mr Gates pleaded guilty to making false statements after being indicted by Mr Mueller and took a plea deal. Defence lawyers have sought to paint Mr Gates as an untrustworthy business partner who dealt with the funds from Mr Manafort's consulting firm.

Mr Mueller has indicted or secured guilty pleas from 32 people and three companies as part of his investigation. President Trump has repeatedly called Mueller's investigation a witch hunt and on Tuesday, he called on Attorney General Jeff Sessions to end it.

Additional reporting by AP and Reuters