Cohen raid 'doesn't have to do with me' - Trump

US President Donald Trump has distanced himself from the legal troubles of his longtime personal lawyer Michael Cohen, saying he has done nothing wrong and Mr Cohen did only fraction of his overall legal work.

"This doesn't have to do with me. Michael is a businessman. He's got a business. He also practices law," Mr Trump said in an interview with Fox News.

"And they're looking at something having to do with his business. I have nothing to do with his business."

Asked how much legal work Mr Cohen did for him, Trump said: "As a percentage of my overall legal work, a tiny, tiny little fraction."

Mr Trump said Mr Cohen represented him in the "crazy" Stormy Daniels case. She is an adult-film star who says she had a one-night stand with Trump in 2006.

Mr Trump has denied having an affair with Ms Daniels or any knowledge of a US$130,000 payment made by Mr Cohen to Ms Daniels before the 2016 US election.

In a filing in Los Angeles federal court on Wednesday, Mr Cohen said he decided to assert his constitutional right after the FBI raided his home, office and hotel room two weeks ago.

"Based on the advice of counsel, I will assert my fifth Amendment rights in connection with all proceedings in this case due to the ongoing criminal investigation by the FBI and US Attorney for the Southern District of New York," Cohen wrote in the filing.

The fifth amendment to the US Constitution states that no individual can be "compelled in any criminal case to be a witness against himself."

By asserting that right, Mr Cohen can avoid revealing information in Ms Daniels' civil lawsuit that could aid federal investigators in the criminal probe of his business dealings.

Ironically, on the campaign trail Mr Trump said innocent people don't plead the fifth, and that it was only for "mobsters".

Elsewhere in the interview, he took aim at "lying" James Comey, the FBI and the Justice Department.

He defended Ronny Jackson, his embattled former nominee to head the Veterans Administration. Mr Trump called allegations of alcohol abuse and other questionable behaviour that have surfaced about Jackson "a disgrace" but confirmed that he is no longer a candidate to head the VA.

Mr Trump said he had a new nominee in mind but would not disclose the name other than to say it would be "somebody with political capability".

With Mr Comey, the FBI director fired amid the chaos of Mr Trump's first few months in the White House, Mr Trump reiterated his assertion: "I did a great thing for the American people by firing him. Comey is a leaker and a liar. He's been leaking for years."

Mr Trump once again decried the "witch hunt" in Washington signified by Mueller's probe. "There's no collusion with me and the Russians. Nobody's been tougher to Russia than I have."

Reuters / Newshub.