Donald Trump's former personal lawyer, Michael Cohen, has been sentenced to three years in prison for his role in making illegal hush-money payments to women to help the President's 2016 election campaign.

Key points: Charges included paying Stormy Daniels $130,000 and Karen McDougal $150,000

Charges included paying Stormy Daniels $130,000 and Karen McDougal $150,000 Prosecutors say the payments violated campaign finance laws

Prosecutors say the payments violated campaign finance laws Mr Trump accused Mueller's team of pressuring his former aides to lie about him

He was also found to have lied to Congress about a proposed Trump Tower project in Russia.

"It was my own weakness and a blind loyalty to this man that led me to choose a path of darkness over light," the 52-year-old Cohen told the judge during the sentencing hearing.

"I felt it was my duty to cover up his own dirty deeds," Cohen said, referring to Mr Trump.

US District Judge William Pauley in Manhattan sentenced Mr Cohen to 36 months for the payments, which violated campaign finance law, and to two months for the false statements to Congress.

The two terms will run simultaneously. The judge set March 6 for Cohen's voluntary surrender.

"Somewhere along the way Mr Cohen appears to have lost his moral compass," Judge Pauley said.

"His cooperation does not wipe the slate clean."

Mr Cohen admitted he lied to Congress about the timeline for discussions about plans for real estate businessman Mr Trump's proposed skyscraper in Moscow. ( AP: Julio Cortez )

The sentencing capped a stunning about-face by a lawyer who once said he would "take a bullet" for Mr Trump, but has now implicated the Republican President in criminal conduct.

Cohen said in his guilty plea in August he was directed by Mr Trump to make hush-money payments to two women who said they had sexual affairs with Mr Trump in the past.

Federal prosecutors in New York said that Cohen, just before the November 2016 election, paid adult film actress Stormy Daniels $US130,000 ($180,000) and helped arrange a $US150,000 ($208,000) payment to former Playboy model Karen McDougal so the women would keep quiet.

Federal law requires that the contribution of "anything of value" to a campaign must be disclosed, and an individual donation cannot exceed $US2,700 ($3,700).

Mr Trump has denied the affairs and any involvement in the payments.

In another potentially worrisome legal development for Mr Trump, prosecutors in New York announced a deal that saw the publisher of the National Enquirer tabloid newspaper avoid charges over its role in paying the hush money Ms McDougal.

Ms McDougal has said she sold her story about the Trump affair to American Media Inc (AMI) but it was never published — it is a practice known as "catch and kill", to prevent a potentially damaging article from being published.

In a statement, the US Attorney's Office for the Southern District said it agreed not to prosecute AMI after the company admitted "that it made the $US150,000 payment in concert with a candidate's presidential campaign, and in order to ensure that the woman did not publicise damaging allegations about the candidate before the 2016 presidential election".

AMI's chief executive officer David Pecker is a longtime friend of Mr Trump and Cohen.

'Cohen today … Trump next'

Michael Cohen arrives for his sentencing at a Manhattan court. ( Reuters: Jeenah Moon )

Daniels' lawyer Michael Avenatti attended the sentencing hearing and said his pursuit of Mr Trump would continue.

"Michael Cohen is neither a hero, nor a patriot," Mr Avenatti said.

"He lied for months on end about his criminal conduct and the role of the president of the United States.

"Michael Cohen was sentenced today. Donald Trump is next. Thank you."

Cohen walked into court on Wednesday morning (local time) with his wife, son and daughter amid a crowd of photographers and reporters.

His family members cried in the courtroom following the sentencing.

"While Mr Cohen pledges to help in further investigations, that is not something the court can consider now," Judge Pauley said.

Threat to Trump presidency increasing

Donald Trump with his then personal attorney Michael Cohen at an election campaign stop in 2016. ( Reuters: Jonathan Ernst )

The three-year sentence was a modest reduction from the four to five years recommended under federal guidelines, but still underscored the seriousness of the charges of violating campaign finance laws and seeking to influence the outcome of an election.

As part of the sentence, the judge ordered Cohen to forfeit $US500,000 ($692,000) and pay restitution of nearly $US1.4 million ($1.9 million).

Cohen pleaded guilty in August to charges including tax evasion, bank fraud and campaign finance violations in a case brought by federal prosecutors in New York.

Cohen was sentenced on a separate charge of lying to Congress brought by special counsel Robert Mueller, who is investigating Russia's role in the 2016 election and possible coordination between Mr Trump's campaign and Moscow.

Cohen pleaded guilty to that charge last month.

The ongoing Mueller investigation represents a threat to Mr Trump's presidency.

Mr Mueller, who also is examining whether the President has unlawfully sought to obstruct the probe, has secured guilty pleas from several former Trump aides including his former campaign chairman and national security adviser, and has brought charges against some Russian nationals and entities.

Reuters/ABC