U.S. President Donald Trump on Friday commuted the sentence of longtime friend and former political adviser Roger Stone days before Stone was set to report to prison to serve a 40-month sentence, according to the White House.

The move came Saturday, just days before Stone was to begin serving a 40-month prison sentence for lying to Congress, witness tampering and obstructing the House investigation into whether Trump's campaign colluded with Russia to win the 2016 election.

"Roger Stone is a victim of the Russia Hoax that the Left and its allies in the media perpetuated for years in an attempt to undermine the Trump Presidency. There was never any collusion between the Trump Campaign, or the Trump Administration, with Russia," said Kayleigh McEnany, the White House press secretary in a statement, and declared "Roger Stone is now a free man!" 

McEnany called the prosecution against Stone a "witch hunt" and said: "Roger Stone has already suffered greatly. He was treated very unfairly, as were many others in this case. Roger Stone is now a free man!"

Stone, 67, was convicted in November last year on seven counts of lying to Congress, tampering with a witness, and obstructing the House investigation into whether the Trump campaign coordinated with Russia to sway the 2016 election. He had been set to report to prison on Tuesday after a federal appeals court rejected his bid to postpone his surrender date. 

A commutation does not erase Stone's criminal conviction as a pardon, but it would protect him from serving prison time as a result.

That 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. Barr told people he was considering resigning over the matter.

House of Representatives Intelligence Committee Chairman Adam Schiff said, "With this commutation, Trump makes clear that there are two systems of justice in America: one for his criminal friends, and one for everyone else."

Stone was the sixth Trump aide or adviser to have been convicted of charges brought during Mueller's investigation. He also was among several Trump associates charged with crimes in former Special Counsel Robert Mueller's investigation that documented Russian interference in the 2016 election to boost Trump's candidacy.

(With input from agencies)