WASHINGTON, June 4 (Reuters) - President Donald Trump's former campaign manager, Paul Manafort, who has been indicted by U.S. Special Counsel Robert Mueller, attempted to tamper with potential witnesses, Mueller said in a court filing on Monday.

Mueller, who is investigating possible collusion between the Trump campaign and Russia, asked the judge overseeing the case in U.S. District Court for the District of Columbia to revoke or revise an order releasing Manafort ahead of his trial. (Reporting by Eric Beech; Editing by Sandra Maler)