A witness who testified before a federal grand jury that handed down indictments of top Trump associates says the president can't get a fair shake and compared the jury room to a Bernie Sanders rally.

The witness claimed two of 20 jurors were wearing 'peace T-shirts,' and popped off on the jury pool to the New York Post's Page Six.

'The grand jury room looks like a Bernie Sanders rally,' the witness said. 'Maybe they found these jurors in central casting, or at a Black Lives Matter rally in Berkeley,' said the witness.

'There was only one white male in the room, and he was a prosecutor,' said the source.

Bernie Sanders supporters gather near City Hall on day three of the Democratic National Convention (DNC) on July 27, 2016 in Philadelphia, Pennsylvania

The person said of 20 jurors, 11 are African-American.

That figure closely mirrors the racial composition of Washington, D.C., which is 49 per cent black. The jury pool, if the source is accurate and correctly identified the racial composition of the panel, is 55 per cent black.

In some cases, D.C. has had difficulty getting juries to match the racial composition of the city, the Washington Post has reported, due to difficulty getting poor minorities to answer the call for jurors and a higher proportion of young black men being eligible due to criminal convictions.

'That room isn't a room where POTUS gets a fair shake,' said the source, using shorthand common in the White House for and D.C. insiders for the president.

A witness said the grand jury that handed down indictments of two Trump associates 'looks like a Bernie Sanders rally.' Sen. Bernie Sanders (I-VT) addresses a rally against the Republican tax plan outside the U.S. Capitol November 1, 2017 in Washington, DC

Bernie Sanders supporters gather near City Hall on day three of the Democratic National Convention (DNC) on July 27, 2016 in Philadelphia

Special counsel Robert Mueller is probing Russian interference in the U.S. elections, and has secured two indictments as well as guilty pleas from Trump campaign officials for lying to the FBI

Former Trump campaign manager Paul Manafort arrives at the Prettyman Federal Courthouse for a hearing December 11, 2017 in Washington, DC. Manafort and his former business partner Richard Gates both pleaded not guilty to a 12-charge indictment that included money laundering and conspiracy

President Trump has repeatedly gone after the Russia probe as a 'witch hunt,' while also attacking the FBI and the Justice Department, which on Tuesday he called part of the 'deep state.'

The source's complaints about the fairness of the grand jury adds the pool of D.C. citizens who meet in secret by law to other institutions that have come under attack during the probe.

But the president indicated to the New York Times over the holidays that he believes he can be treated fairly by Mueller, who has come under attack by House Republicans.

'I have absolute right to do what I want to do with the Justice Department,' Trump told the paper from Mar-a-Lago. 'But for purposes of hopefully thinking I'm going to be treated fairly, I've stayed uninvolved with this particular matter,' he said.

The grand jury has already handed down two indictments of Trump associates, former campaign chair Paul Manafort, and his deputy, Rick Gates.