US President Donald Trump has commuted the prison sentence for long-time friend and adviser Roger Stone, who was jailed for lying to Congress during the Russia probe, the White House says.

“Roger Stone has already suffered greatly,” the White House said in a statement.

“He was treated very unfairly, as were many others in this case. Roger Stone is now a free man.”

Stone, 67, was scheduled to report by Tuesday to a federal prison in Jesup, Georgia, to begin serving a sentence of three years and four months for lying under oath to US politicians investigating Russian interference in the 2016 US election.

The White House later confirmed the commuting of the sentence in a statement, saying Stone was a victim of the Russia “hoax.”

The move, though short of a full pardon, is sure to alarm critics who have long railed against the president’s repeated interventions in the nation’s justice system.

“The President told me he thought my trial has been unfair,” Stone said in a phone call from Fort Lauderdale, Florida. Stone said he expressed his gratitude and was popping champagne.

Stone had been sentenced in February to three years and four months in prison for lying to Congress, witness tampering and obstructing the House investigation into whether the Mr Trump campaign colluded with Russia to win the 2016 election. He was set to report to prison by Tuesday.

A commutation would not erase Stone’s felony convictions in the same way a pardon would, but it would protect him from serving prison time as a result.

Tweet from @CBS_Herridge

The action, which Mr Trump had foreshadowed in recent days, reflects his lingering rage over the Russia investigation and is a testament to his conviction that he and his associates were mistreated by agents and prosecutors.

His administration has been eager to rewrite the narrative of special counsel Robert Mueller’s Russia investigation, with Trump’s own Justice Department moving in May to dismiss the criminal case against former national security adviser Michael Flynn.

Stone, for his part, had been open about his desire for a pardon or commutation, appealing for the President’s help in a series of Instagram posts in which he maintained that his life could be in jeopardy if imprisoned during a pandemic. He had recently sought to postpone his surrender date by months after getting a brief extension from the judge.

Mr Trump had repeatedly publicly inserted himself into Stone’s case, including just before Stone’s sentencing, when he suggested in a tweet that Stone was being subjected to a different standard than several prominent Democrats. He railed that the conviction “should be thrown out” and called the Justice Department’s initial sentencing recommendation “horrible and very unfair.”

“Cannot allow this miscarriage of justice!” he wrote.

Stone, a larger-than-life political character who embraced his reputation as a dirty trickster, was the sixth Trump aide or adviser to have been convicted of charges brought as part of Mr Mueller’s investigation into Russian interference in the 2016 election.

A longtime friend of Mr Trump and informal adviser, Stone had boasted during the campaign that he was in contact with WikiLeaks founder Julian Assange through a trusted intermediary and hinted at inside knowledge of WikiLeaks’ plans to release more than 19,000 emails hacked from the servers of the Democratic National Committee.

But Stone denied any wrongdoing and consistently criticised the case against him as politically motivated. He did not take the stand during his trial, did not speak at his sentencing, and his lawyers did not call any witnesses in his defence.

Trump also targeted those involved in the case. He retweeted a comment by Fox News commentator Andrew Napolitano that the jury appeared to have been biased against Mr Trump, and called out Judge Amy Berman Jackson by name, saying “almost any judge in the country” would throw out the conviction.

Tweet from @realDonaldTrump

The tweets continued even after Mr Trump earned a public rebuke from his own attorney general, William Barr, who said the president’s comments were “making it impossible” for him to do his job. Mr Barr was so incensed that he told people he was considering resigning over the matter.

-with agencies