US Attorney General Bill Barr on Thursday delivered a highly unusual public rebuke of Donald Trump, saying the president's tweets were making his job at the Justice Department "impossible."

"I have a problem with some of the tweets," Barr said in an interview with ABC News, adding: "I cannot do my job here at the department with a constant background commentary that undercuts me."

"I think it's time to stop the tweeting about Department of Justice criminal cases," said Barr.

Barr's interview came as Trump stands accused of interfering with the sentencing recommendation for his former advisor, Roger Stone -- prompting four Justice Department prosecutors to resign from the case this week.

US Attorney General William Barr
US Attorney General William Barr will testify to the House Judiciary Committee on March 31, 2020, amid allegations that he is bending Justice Department policy to help President Donald Trump. Photo: AFP / ANDREW CABALLERO-REYNOLDS

The outburst was all the more remarkable as Barr has emerged as a powerful defender of Trump, earning the nickname of the "president's attorney" from critics.

Barr has been in the eye of the storm over allegations that he decided -- allegedly under pressure from Trump -- to overrule his own prosecutors and seek a lighter prison sentence for Stone.

He has previously been criticised by Democrats and legal experts for seeming to assist Trump during the independent investigation into whether the president was helped by a Russian influence campaign during the 2016 election.

The two men are so close, that there was immediately speculation that Barr's television interview may have been more about managing public opinion than a real outcry against Trump's alleged interference in judicial affairs.

White House spokeswoman Stephanie Grisham said Trump had "full faith" in Barr.

US President Donald Trump
Donald Trump stands accused of interfering with the sentencing recommendation for his former advisor, Roger Stone -- prompting four Justice Department prosecutors to resign from the case. Photo: AFP / JIM WATSON

"The President wasn't bothered by the comments at all," she said in a statement.

That message was amplified by Trump's National Security Advisor who insisted the president has "tremendous confidence" in Barr.

"He's a fantastic member of the cabinet he has a very strong relationship with the president," O'Brien told reporters at the White House.

Roger Stone, former advisor to Trump
Roger Stone, a former advisor to US President Donald Trump, is facing sentencing for lying to Congress about his role in Russian meddling in the 2016 election. Photo: AFP / Andrew CABALLERO-REYNOLDS

Unlike any president before him, Trump frequently uses social media to broadcast his opinions and decisions without going through traditional statements to the media.

Grisham indicated that Barr's comments would not change that, referring to the White House's frequent claim that professional media organizations misrepresent Trump and therefore need to be bypassed.

"President Trump uses social media very effectively to fight for the American people against injustices in our country, including the fake news," she said.

Trump uses Twitter in particular to make instant, high-impact interventions, often reacting to events in real time.

In the latest case, he used his Twitter pulpit to speak out in defense of veteran Republican consultant Stone.

Stone was convicted in November last year of lying to Congress, tampering with a witness and obstructing the House investigation into the Russia 2016 election affair.

Trump has denied that his tweets attacking the original sentence of 87 to 108 months recommended for Stone -- and in support of Barr after it was reduced by more than half -- amounted to political interference.

When asked whether he had spoken with Trump about recommendations in the Stone case, Barr replied: "Never."

"I'm happy to say that in fact the president has never asked me to do anything in a criminal case," said Barr, who is due to testify next month to Congress where Democrats have voiced deep concerns about his conduct in legal matters involving the president.

In the interview, Barr said he had been "surprised" by the sentencing recommendation filed by prosecutors on Monday, and was intending to "amend and clarify" the department's position the following day -- when Trump fired off his tweet.

"Once the tweet occurred the question was, 'Now what do I do?' Do you go forward with what you think is the right decision or do you pull back because of the tweet -- and that just sort of illustrates how disruptive these tweets can be."

Asked whether he was prepared for repercussions for speaking out against Trump, Barr replied: "Of course."

"I'm not going to be bullied or influenced by anybody," he said, "whether it's Congress, newspaper editorial boards, or the president, I'm going to do what I think is right."

Copyright AFP. All rights reserved.