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.
The special counsel said Manafort's alleged actions constituted a violation of the conditions of his release.
The filing says Manafort used encrypted messaging application to try and reach certain witnesses.
One potential witness told the government, according to the filing, that "he understood Manafort's outreach to be an effort to 'suborn perjury'" — that is, an attempt to persuade that witness to commit perjury.
The next step is a response from a federal judge and any filings from Manafort's team. If the judge ultimately decides to revoke his bail, Manafort may be placed in jail until at least his trial later this year.
A spokesman for the special counsel's office told CNBC it declined to comment beyond the court filing at this time. The White House did not immediately respond to CNBC's request for comment, and Manafort's lawyers in the Washington, D.C. case had no immediate comment.
—CNBC's Kevin Breuninger and NBC News contributed to this report.