Paul Manafort has until Friday to respond to allegations of witness tampering

A federal judge will decide whether to jail former Donald Trump campaign chairman Paul Manafort while he awaits trial after prosecutors accused him of making several attempts to tamper with witnesses in his criminal case.

U.S. District Judge Amy Berman Jackson on Tuesday set a hearing for next week and gave Manafort until Friday to respond to the allegations made by special counsel Robert Mueller's team that Manafort and one of his associates "repeatedly" contacted two witnesses in an effort to influence their testimony.

In a statement, Manafort spokesperson Jason Maloni said, "Mr. Manafort is innocent, and nothing about this latest allegation changes our defence. We will do our talking in court."

Manaforthas been under house arrest since he was indicted by Mueller in October.

Mueller's team saidin a new court filing on Monday that Manafort and one of his associates have "repeatedly" contacted two witnesses via phone, text message and encrypted messages in an effort to get them to lie about the nature of lobbying and public relations work they carried out at Manafort's direction on behalf of Ukraine.

Mueller, who is investigating possible collusion between theTrump campaign and Russia, asked the judge overseeing the casein U.S. District Court for the District of Columbia to revoke orrevise an order releasingManafortahead of his trial.

The two witnesses are not named in court filings, but prosecutors say they are connected to the Hapsburg Group, a firm Manafortworked with to promote the interests ofUkraine.

The FBI has documents and statements from the two people, as well as telephone records and documents recovered through a search of Manafort's iCloud account, showing the attempted communication, according toFBI Special Agent Brock Domin, in a declaration filed withMueller's motion.

"Theinvestigation into this matter is ongoing," Dominwrote.

Manafort is the most senior member of Trump's campaign to beindicted, though the charges do not relate to his campaignactivities.

Together with his longtime associate Rick Gates, he is facing two separate indictments on an array ofcharges in federal courts in Virginia and Washington, D.C.

In the latter he is charged with conspiracy to laundermoney, conspiracy against the United States, making false statements, and charges in connection with failing to registeras a foreign agent, despite lobbying in the United States for the pro-KremlinUkrainian government of former presidentViktorYanukovych.

The charges he faces in Virginia includebank fraud and filingfalse tax returns.

He has pleaded not guilty to all charges.

Mueller has recentlybeen dialing up the legal pressure on Manafort, who has opted not to co-operate with investigators.