WASHINGTON (REUTERS) - Under pressure from President Donald Trump, the US Justice Department on Tuesday (Feb 11) abruptly moved to seek a shorter prison sentence for veteran Republican operative and long-time Trump adviser Roger Stone, with all four prosecutors quitting the case after the highly unusual reversal.

Senior department officials - hours after Mr Trump publicly complained that Stone was being treated unfairly - overrode the sentencing recommendation of seven to nine years made on Monday by the federal prosecutors who secured Stone's November conviction.

Stone was found guilty on seven counts of lying to Congress, obstruction and witness tampering.

In a new court filing, a Justice Department official who had not previously worked on the case called that recommendation"excessive and unwarranted" and said the department would not make a formal recommendation.

Democrats blasted the department's shift in the high-profile case involving Stone, whose friendship with Mr Trump dates back decades. Stone's trial arose from former Special Counsel Robert Mueller's investigation that detailed extensive Russian interference in the 2016 election to benefit Mr Trump's candidacy.

Mr Trump told reporters he thought the initial recommendation was 'ridiculous" but said he did not speak to the Justice Department about it.

"I'd be able to do it if I wanted. I have the absolute right to do it. I stay out of things," Mr Trump told reporters. "I thought the recommendation was ridiculous."

A senior Justice Department official, briefing reporters on condition of anonymity, called the timing of Mr Trump's tweet an"inconvenient coincidence."

After the department's action was disclosed, the four prosecutors who won Stone's conviction - Mr Aaron Zelinsky, Mr John Crabb, Mr Michael Marando and Mr Jonathan Kravis - withdrew from the case.

Mr Kravis told the court in a filing he was not only leaving the case but quitting his post as a federal prosecutor.

US district judge Amy Berman Jackson is due to sentence Stone on Feb 20.

Mr Trump also withdrew the nomination of Ms Jessie Liu, a former US attorney in Washington whose office prosecuted Stone, for the post of Treasury undersecretary for terrorism and financial crimes, a source familiar with the matter said

Legal experts described the department's move as highly unusual. Democrats accused Attorney-General William Barr, who heads the department, of working to protect Mr Trump's political interests.

'HELP HIS FRIENDS'

"The president seems to think the entire Justice Department is just his personal lawsuit to prosecute his enemies and help his friends," Mr Chuck Schumer, the top Senate Democrat, told reporters.

Mr Schumer asked the department's internal watchdog to investigate the reversal. Democrat Jerrold Nadler, chairman of the House of Representatives Judiciary Committee, said he also would investigate the matter.

"AG Barr must stop being the President's lapdog. They are turning us into a banana republic," Democratic Senator Chris Van Hollen added on Twitter.

Stone, who has labelled himself a "dirty trickster" and"agent provocateur" and famously has the face of former President Richard Nixon tattooed on his back, was one of several Mr Trump associates charged with crimes as part of Mr Mueller's investigation.

In a court filing on Monday, prosecutors said their proposed sentence fell within US guidelines and would "accurately reflect the seriousness of his crimes and promote respect for the law."

That came as a surprise to senior Justice Department officials who were expecting prosecutors to ask for a lower range, said an official who spoke on condition of anonymity. The Justice Department was not in touch with the White House over the matter, the official said.

Legal experts said it would be unusual for prosecutors to change their proposed sentence after filing a formal recommendation to the court, especially on a high-profile case like this in which senior Justice Department officials as well as courtroom prosecutors are involved in the decision-making.

Several said that the proposed sentence struck them as unusually severe. Stone's defence team, in a filing late on Monday, disputed the prosecution's calculation and proposed a range of between 15 and 21 months. They asked the judge for a sentence that would fall below that range.

"It is high, but the prosecutors obviously felt there were extenuating circumstances that justified the enhancements," said Ms Lynn Niels, a former federal prosecutor.

The new Justice Department filing noted that Stone's guideline sentence would be significantly less - about three to four years - if the charge that he threatened a witness, Mr Randy Credico, was not used in the calculation.

Stone was convicted of the charge. The position taken by the department on the witness tampering charge echoed arguments made by Stone's own defence team in their memo filed late on Monday.

Mr Mueller's investigation detailed a Russian campaign of hacking and propaganda in the 2016 election and extensive contacts between the president's campaign and Moscow. Stone was one of only two of these Trump associates who went to trial rather than pleading guilty.

Mr Trump has the power to pardon people for federal crimes, although he has yet to use it in the cases of other former aides convicted in the wake of the Mueller investigations.