WASHINGTON (Reuters) - A senior aide to U.S. President Donald Trump on Sunday assailed a new book rattling the White House, called his boss a genius and launched an attack on news coverage before a TV anchor urged him to calm down and cut off their interview.

Senior policy adviser Stephen Miller told Jake Tapper on CNN’S “State of the Union” that the book “Fire and Fury: Inside the Trump White House” by journalist Michael Wolff was a “grotesque work of fiction.”

Miller accused CNN of “anti-Trump hysterical coverage” following the Friday release of the book, which portrays Trump, a former reality TV start who took office nearly a year ago, as mentally unstable and unfit for the demands of his job.

“The reality is that the president is a political genius,” Miller said and accused Tapper of being “condescending” and “snide.”

“I have no idea why you’re attacking me,” Tapper responded, saying Miller was being “obsequious” and asking him to “calm down” before cutting the interview short.

“I think we have wasted enough of my viewers’ time,” Tapper said, ending the interview.

The White House has been on the defensive since excerpts of the book were published last week with the president and his aides scrambling to discredit both its portrayal of Trump and the author’s methods.

Its publication prompted Trump to post on Twitter on Saturday that he is a “very stable genius.” The president attacked the book again on Sunday.

Wolff was granted unusually wide access to the White House during much of Trump’s first year at the behest of former Trump strategist Steve Bannon, who advised the president during his first months in office and during his presidential campaign.

Wolff has said the book was based on White House access, conversations with Trump and interviews with senior staffers, including Bannon.

“It is tragic and unfortunate that Steve would make these grotesque comments,” Miller said on CNN.

Wolff appeared on NBC’s “Meet the Press” on Sunday and defended his portrayal of Trump in the book, along with his reporting methods.