Steve Bannon tries to make amends as aides mobilised to defend Donald Trump

But Mr Bannon said today his description was aimed at former Trump campaign chairman Paul Manafort, who also attended the meeting, and not Mr Trump's son.

"I regret that my delay in responding to the inaccurate reporting regarding Don Jr has diverted attention from the president's historical accomplishments in the first year of his presidency," Mr Bannon said in the statement, first obtained by the news site Axios.

He said his support for Mr Trump and his agenda was "unwavering".

Hours before the statement came out, administration officials used appearances on the Sunday news shows to rally behind Mr Trump and try to undermine Wolff's Fire and Fury: Inside the Trump White House, which portrays the 45th president as a leader who does not understand the weight of his office and whose competence is questioned by aides.

Chief policy adviser Stephen Miller, in a combative appearance on CNN, described the book as "nothing but a pile of trash through and through".

He also criticised Mr Bannon, who is quoted at length by Wolff, saying it was "tragic and unfortunate" that Mr Bannon "would make these grotesque comments so out of touch with reality and obviously so vindictive".

CIA director Mike Pompeo said Mr Trump was "completely fit" to lead the country, pausing before answering because, he said on Fox News Sunday, it was such "a ludicrous question".

"These are from people who just have not accepted the fact that President Trump is the United States' president and I'm sorry for them in that," said Mr Pompeo, who gives Mr Trump his regular intelligence briefings.

Nikki Haley, the US ambassador to the United Nations, said that she was at the White House once a week, and "no one questions the stability of the president".

"I'm always amazed at the lengths people will go to, to lie for money and for power. This is like taking it to a whole new low," she told ABC's This Week.

Stephen Miller said "the portrayal of the president in the book is so contrary to reality, to the experience of those who work with him".

Mr Miller's interview on CNN's State of the Union quickly grew heated, with Mr Miller criticising CNN's coverage and moderator Jake Tapper pressing him to answer his questions and accusing him of speaking to only one viewer: Mr Trump.

Mr Tapper abruptly ended the interview, saying: "I think I've wasted enough of my viewers' time."

Soon after, Mr Trump tweeted: "Jake Tapper of Fake News CNN just got destroyed in his interview with Stephen Miller of the Trump Administration. Watch the hatred and unfairness of this CNN flunky!"

Mr Trump used Twitter on Saturday to defend his fitness for office, insisting he was "like, really smart" and, indeed, a "very stable genius".

He pressed the case again today as he prepared to depart Camp David for the White House.

"I've had to put up with the Fake News from the first day I announced that I would be running for President. Now I have to put up with a Fake Book, written by a totally discredited author," he tweeted.

Mr Wolff's book draws a derogatory portrait of Mr Trump as an undisciplined man-child who did not actually want to win the White House and who spends his evenings eating cheeseburgers in bed, watching television and talking on the telephone to old friends.

The book also quotes Mr Bannon and other prominent advisers as questioning the president's competence.

Mr Trump and some aides have attacked Mr Wolff's credibility, pointing to the fact that the book includes a number of factual errors and denying that the author had as much access as he claimed.

- AP