WASHINGTON - The chairman of the US Senate Judiciary Committee has vowed to investigate allegations that top FBI and justice department officials discussed ways to remove President Trump from office.

Senator Lindsey Graham said the claims were an "attempted bureaucratic coup".

Ex-acting FBI chief Andrew McCabe said Deputy Attorney General Rod Rosenstein had talks in 2017 about a constitutional clause that allows the removal of a president if deemed unfit.

Mr Rosenstein has previously denied it.

The pledge by Mr Graham, a Republican who has become one of the president's biggest defenders, comes after Mr McCabe appeared on US broadcaster CBS saying Mr Rosenstein discussed the numbers needed to invoke the clause, known as the 25th Amendment to the US constitution.

In the 60 Minutes interview aired on Sunday, Mr McCabe also said that:

The FBI "had reason to investigate" the president's links with Russia, based on Mr Trump's actions
Mr Rosenstein had been "absolutely serious" when he discussed secretly wearing a wire to record Mr Trump
Mr Trump said Russian President Vladimir Putin had told him North Korea did not have the capability to hit the US with ballistic missiles - and, when US intelligence officials contradicted this assessment, responded with: "I don't care. I believe Putin"
The White House said Mr McCabe, who was fired last year for allegedly lying to government investigators, had "no credibility".

The allegations that Mr Rosenstein discussed invoking the amendment were first reported last year by the New York Times, which cited anonymous sources.(FA)