A new book claims that Vice President Pence was asked to be on standby while President Trump was visiting Walter Reed Hospital in 2019, CNN reports.

In Michael S. Schmidt’s Donald Trump v. the United States: Inside the Struggle to Stop a President, Schmidt writes, “In the hours leading up to Trump’s trip to the hospital, word went out in the West Wing for the vice president to be on standby to take over the powers of the presidency temporarily if Trump had to undergo a procedure that would have required him to be anesthetized.”

The Guardian reports that novelist Don Winslow, who has been vocal in his opposition to Trump, says that he’s been told by anonymous sources that Trump suffered multiple “mini-strokes.”

Trump denied that on Twitter, writing, “It never ends! Now they are trying to say that your favorite President, me, went to Walter Reed Medical Center, having suffered a series of mini-strokes. Never happened to THIS candidate - FAKE NEWS. Perhaps they are referring to another candidate from another Party!”

On Fox News, Pence denied the report, saying, “I don't recall being told to be on standby. I was informed that the President had a doctor's appointment.”

A reviewer for Kirkus called Donald Trump v. the United States “a detailed, deeply reported portrait of a president willfully obstructing justice—with plenty of help.” The book was published on Wednesday.

Michael Schaub is a Texas-based journalist and regular contributor to NPR.