Trump tweets make my job 'impossible', says Attorney-General William Barr

Donald Trump's top lawman has publicly criticised the US president over his Twitter commentary on ongoing legal cases.

Attorney-General William Barr, who has gained a reputation as one of the president's most vociferous defenders, made the striking comments in an interview with US network ABC.

"The president has never asked me to do anything in a criminal case," Mr Barr said.

"However to have public statements and tweets made about the department, about people in the department, about cases pending in the department, and about judges before whom we have cases, make it impossible for me to do my job."

The comments come as the Justice Department pushes for a lighter sentence for close Trump ally Roger Stone, who is facing up to nine years prison for obstruction and witness tampering.

After the call for leniency for Stone, all four prosecutors involved in the case resigned in protest.

Mr Trump has tweeted repeatedly about Stone, leading to speculation that the president was behind the push for leniency.

In the past two days on Twitter Mr Trump has attacked the foreperson of Stone's jury, "rogue prosecutors", special counsel Robert Mueller, the prosecutors in the case, and the judge.

Kelly speaks out

Donald Trump's former chief-of-staff John Kelly has also broken his silence about his concerns.

General Kelly criticised the president on a number of issues, including pardoning a Navy SEAL convicted of war crimes.

He also took umbrage at Mr Trump characterising Mexican immigrants as rapists and criminals.

"In fact, they're overwhelmingly good people," Gen. Kelly said.

"They're not all rapists and they're not all murderers. And it's wrong to characterise them that way. I disagreed with the president a number of times."

Mr Trump lashed out at Gen. Kelly overnight on Twitter.

"When I terminated John Kelly, which I couldn't do fast enough, he knew full well that he was way over his head.

"Being Chief of Staff just wasn't for him. He came in with a bang, went out with a whimper, but like so many X's, he misses the action & just can't keep his mouth shut."