US President Donald Trump’s former campaign chairman Paul Manafort has been sentenced to prison after he was accused of witness tampering in his conspiracy trial.

Mr Manafort, a businessman and political lobbyist, is a central figure in the investigation into Russian meddling in the 2016 election and was on bail for a raft of charges including money laundering and conspiracy against the United States.

The 69-year-old had his bail revoked on Saturday (Friday local time) and was sentenced to jail pending a September trial by a judge in Washington after it was alleged he contacted government witnesses in an effort to get them to lie to investigators.

“I have no appetite for this, but in the end, I cannot turn a blind eye,” US District Judge Amy Berman Jackson said, revoking his bail after already serving seven months in home detention. “You’ve abused the trust placed in you.”

According to the Washington Post, Judge Berman Jackson described the decision to send Mr Manafort to prison as “extraordinarily difficult” but said his behaviour – which allegedly included ghost-writing an opinion piece defending his behaviour in an English-speaking newspaper in Ukraine – left her with little choice.

Donald Trump’s former campaign manager Paul Manafort (r) has been named but denies any contact with Russian officials. Photo: Getty

In 2016, Mr Manafort served as Mr Trump’s campaign chairman during the Republican National Convention and has a history as a confidant to Republican presidents dating back decades.

Mr Manafort was indicted by Special Counsel Robert Mueller – the head of the investigation in Russian meddling in the US election – in February for failing to declare the decade he spent as a lobbyist for a pro-Russian former politician and party in Ukraine.

His Ukraine consulting reportedly netted him $US30 million ($40.2 million) in secret cash payments over a nine-year period, which he then allegedly laundered.

On June 8, Mr Mueller brought fresh charges against Mr Manafort and a Russian associate, alleging Mr Manafort contacted two government witnesses the day after his indictment and sustained a five-week campaign asking them to tell investigators his lobbying in Ukraine did not involve the United States.

Mr Manafort has pleaded not guilty to the witness tampering charges and will be detained in prison until his September trial. His lawyers have also denied the allegations.

President Trump on Friday sought to downplay his connection to Mr Manafort and told reporters he felt sorry him.

“[He] has nothing to do with our campaign, but I tell you I feel a little badly about it,” Mr Trump said. “They went back 12 years to get things that he did 12 years ago.”

Mr Trump said Mr Manafort worked for him for “a very short period of time”.

The fresh obstruction charge against Mr Manafort is the latest development in Mr Mueller’s sustained investigation into collusion between the Russian government and the Trump campaign.

Ebony Bowden reported from New York City.