A pardon for Donald Trump’s former campaign chairman Paul Manafort is “not off the table”, the president has said, prompting fears he will use his executive power to protect friends and supporters caught up in the Russia probe.

The president’s discussion of a possible pardon in an interview with the New York Post came days after special counsel Robert Mueller said Manafort had breached his plea deal by repeatedly lying to investigators.

Manafort denies that he lied.

Mr Trump’s remarks are the latest sign of his disdain for the Russia investigation, which has dogged him for two years and ensnared members of his inner circle.

While the disgusting Fake News is doing everything within their power not to report it that way, at least 3 major players are intimating that the Angry Mueller Gang of Dems is viciously telling witnesses to lie about facts & they will get relief. This is our Joseph McCarthy Era! — Donald J. Trump (@realDonaldTrump) November 28, 2018

In recent weeks, the president, armed with inside information provided to his lawyers by Manafort’s legal team, has sharpened his attacks, seizing on what he claims are dirty tactics employed by the special counsel and accusing investigators of pressuring witnesses to lie.

In the interview, Mr Trump likened the Russia probe to senator Joe McCarthy’s pursuit of communists in the 1950s.

“We are in the McCarthy era. This is no better than McCarthy,” he told the newspaper.

Asked about a pardon for Manafort, Mr Trump said: “It was never discussed, but I wouldn’t take it off the table. Why would I take it off the table?”

Trump threatens to declassify 'devastating' docs about Democrats https://t.co/7u59BMFTtL pic.twitter.com/AGfwK0VCsP — New York Post (@nypost) November 28, 2018

He only has the power to pardon for federal charges. A pardon would not shield Manafort from prosecution for state charges, although he is not currently facing any.

On Wednesday, the top Democrat on the Senate intelligence committee said that if Mr Trump pardons Manafort, it would be a “blatant and unacceptable abuse of power”.

Senator Mark Warner said in a tweet that the president’s pardon power is not a “personal tool” he can use to protect “himself and his friends”.

Manafort’s lawyers have been briefing Trump lawyers in recent months on what their client has told investigators, an unusual arrangement for a government co-operator and one that raises the prospect that Manafort could be angling for a pardon.

In the Post interview, Mr Trump also praised two other supporters caught up in the Russia probe — conservative author and conspiracy theorist Jerome Corsi and long-time Trump associate Roger Stone.

He said they were “very brave” for resisting Mr Mueller’s investigation.

Both men have been heavily critical of the investigation, and Corsi this week said he had rejected a plea offer from Mr Mueller’s team. Draft plea documents show Mr Mueller accusing Corsi of lying to investigators — an allegation he denies — about emails he exchanged with Stone regarding WikiLeaks.

US intelligence agencies believe Russia was the source of hacked material from Democratic organisations that WikiLeaks released during the 2016 presidential campaign.

That included thousands of stolen emails from the private account of Hillary Clinton campaign chairman John Podesta in the closing weeks of the campaign.

Mr Mueller is investigating whether any Trump associates had advance knowledge of WikiLeaks’ plans.

The special counsel earlier this week said Manafort could face additional charges related to lies he allegedly told investigators in the nearly three months since he cut a plea deal.

Neither Manafort nor Mr Mueller’s team has said what Manafort is accused of lying about, but a federal judge set a hearing for Friday in which she will hear from both sides about next steps in the case.

That hearing could yield new details about the status of the Russia probe.

Manafort faces up to five years in prison on the two charges in his plea agreement — conspiracy against the US and conspiracy to obstruct justice. He faces a separate sentencing in Virginia in February after he was convicted on eight felony counts during a trial last summer.

- Press Association