NEW YORK (REUTERS) - Michael Cohen, United States President Donald Trump's former personal lawyer, took a parting shot at his ex-boss - denouncing "xenophobia, injustice and lies" - before reporting to a federal prison on Monday (May 6) to begin a three-year sentence.

Cohen - who once vowed to "take a bullet" for Mr Trump, but now calls him a "con man" - checked into the Federal Correctional Institution in Otisville, New York, about 110km north-west of New York City, to serve his sentence for arranging hush payments to two women who said they had sexual encounters with Mr Trump, financial crimes and lying to Congress.

Cohen, 52, hinted he had more secrets to divulge as he made brief remarks to a crush of camera crews and reporters gathered on the sidewalk outside his Manhattan residence - the Trump Park Avenue apartment building - before being driven to the prison.

"I hope that when I rejoin my family and friends, the country will be in a place without xenophobia, injustice and lies at the helm of our country," he said, without uttering Mr Trump's name. "There still remains much to be told and I look forward to the day that I can share the truth."

Cohen was driven to the prison in a black sport utility vehicle (SUV), arriving shortly after 11.30am (11.30pm Singapore time), some 2½ hours before his deadline to report. Aerial TV news video showed him stepping out of the SUV, then removing his jacket and leaving it inside the vehicle before walking with two men, apparently prison officials, into a building entrance.

The US Bureau of Prisons, which runs the facility, confirmed by e-mail that Cohen was in its custody. He is expected to stay at the prison's minimum security camp.

Cohen's prison term completes a stunning fall for the native of New York's Long Island, whose career was tethered to Mr Trump as he evolved from a wealthy real estate developer to reality television personality to politician.

For more than a decade, Cohen served as Mr Trump's personal lawyer and self-described "fixer". Mr Trump has blasted Cohen, calling him a "rat" as well as a "bad lawyer and fraudster".

Cohen, who has been disbarred as an attorney, was dressed in jeans, sneakers, a white shirt and a navy blue blazer as he exited his apartment building, with a doorman holding the door. Several dozen bystanders stopped to take pictures and one shook his hand.

After Cohen made his remarks, the scene became chaotic, with equipment and people falling to the ground. Cohen helped one journalist to get back on his feet. He then climbed into the SUV.

FBI agents in April 2018 raided his Rockefeller Center office and Park Avenue hotel room as part of an investigation that grew out of Special Counsel Robert Mueller's investigation into Russian interference in the 2016 US election. That set in motion events that caused Cohen's dramatic split with Mr Trump.

'TELL THE TRUTH'

Mr Lanny Davis, spokesman for Cohen, issued a statement saying Cohen "will continue to be accessible to Congress and to federal, state and local law enforcement".

"I will continue questioning why Michael is the only person within the Trump Organisation to be prosecuted for crimes committed at the direction of and for the benefit of Mr Trump," Mr Davis added.

He praised Cohen's "courageous decision ... to tell the truth about why Donald Trump represented a danger to our Constitution, our freedoms and our nation's fundamental values".

Cohen had originally been due to report to prison on March 6, but was granted an extension to recover from shoulder surgery and testify before Congress. He broke with Mr Trump in July 2018, telling ABC News he intended to put family and loyalty to his country ahead of the President.

Cohen and his wife Laura Shusterman, 49, have two adult children, Samantha and Jake.

In the February congressional testimony, he said: "I am ashamed that I chose to take part in concealing Mr Trump's illicit acts rather than listening to my own conscience. I am ashamed because I know what Mr Trump is. He is a racist. He is a con man. He is a cheat."

During his December sentencing in New York, Cohen said, "My weakness can be characterised as blind loyalty to Donald Trump and I was weak for not having the strength to question and to refuse his demands."

Cohen pleaded guilty to violating campaign finance law, bank fraud and tax evasion. Prosecutors said Mr Trump himself directed illegal hush payments orchestrated by Cohen of US$130,000 (S$177,000) to adult film star Stormy Daniels and US$150,000 to Playboy model Karen McDougal to avert a scandal shortly before the 2016 election.

Mr Trump has denied sexual relationships with them and said he never directed Cohen to do anything illegal.

Cohen also pleaded guilty to lying to Congress about a proposed Trump tower project in Russia that was being negotiated at the same time he was running for president. His prison time could be reduced by about 15 per cent for good behaviour.