US President Donald Trump did not have a stroke and remains healthy, says his doctor after a new book suggesting Vice-President Mike Pence was placed on standby during a sudden Trump medical visit last year.

Donald Trump v The United States cites a claim by New York Times reporter Michael Schmidt that word went out in the West Wing in November for Mr Pence to be ready if Mr Trump had to undergo a procedure requiring him to be anaesthetised.

The White House has declined to comment on the assertion.

However Mr Trump and his physician did appear to respond on Tuesday (local time) to author Don Winslow’s posting on Twitter last month that he received three communications from administration whistleblowers that Mr Trump had had “a series of mini-strokes”.

Tweet from @realDonaldTrump

“I can confirm that President Trump has not experienced nor been evaluated for a cerebrovascular accident (stroke), transient ischemic attack (mini stroke), or any acute cardiovascular emergencies, as have been incorrectly reported in the media,” Dr Sean Conley said in a statement.

“The president remains healthy and I have no concerns about his ability to maintain the rigorous schedule ahead of him.

“As stated in my last report, I expect him to remain fit to execute the duties of the Presidency,” Dr Conley added.

On Twitter, Mr Trump also denied having suffered a series of mini-strokes.

Tweet from @realDonaldTrump

At the time, the White House described Mr Trump’s unexpected and unscheduled visit to Walter Reed National Military Medical Centre as a start to his annual physical that included a quick exam and some laboratory tests.

But the trip triggered questions on social media since it occurred months before the annual physical had been conducted in the past.

Mr Trump, known for his love of hamburgers and well-done steaks and an aversion to the gym, gained weight from his physical in 2017, pushing his body mass index into the obese category.

-AAP