United States President Donald Trump on Wednesday dismissed a book written by The Washington Post journalist Bob Woodward, as “lies and phony”. The book, Fear: Trump in the White House, is highly critical of the president and is scheduled to be released on September 11. Woodward was one of the reporters who exposed the Watergate scandal that ended Richard Nixon’s presidency in 1974.

Woodward quotes White House aides who claimed to have saved the United States by ignoring Trump’s orders on several occasions and even stealing his documents, CNN reported. The author claimed Chief of Staff John Kelly described Trump as an “idiot”. “It’s pointless to try to convince him of anything,” Kelly is quoted as saying.

Defence Secretary James Mattis reportedly told his associates that Trump has the understanding of a “fifth or sixth grader.” The book claims that the president questioned why the US has to have a large troop presence in South Korea. “We are doing this in order to prevent World War III,” the book quotes Mattis telling Trump at a meeting in January.

Trump took to Twitter to criticise the book. “The already discredited Woodward book, so many lies and phony sources, has me calling [Attorney General] Jeff Sessions ‘mentally retarded’ and ‘a dumb southerner’, Trump tweeted. “I said neither, never used those terms on anyone, including Jeff, and being a southerner is a GREAT thing. He made this up to divide!”

Trump also posted statements from Mattis, Kelly and White House spokesperson Sarah Huckabee Sanders refuting the claims made in the book. “The idea that I ever called the President an idiot is not true,” Trump quoted Kelly’s statement. “This is another pathetic attempt to smear people close to President Trump”

Mattis also said the quote attributed to him was false. “The contemptuous words about the president attributed to me in Woodward’s book were never uttered by me or in my presence,” Mattis said in a statement. “While I generally enjoy reading fiction, this is a uniquely Washington brand of literature, and his anonymous sources do not lend credibility.”

The Washington Post on Tuesday published a recording of a purported phone conversation between Trump and Woodward where the president is heard saying “you’ve always been fair”. Woodward was reportedly denied access to the President until he completed his book and allowed only a phone conversation with him.

On August 30, Trump had accused journalist Carl Bernstein, who was part of the team that exposed the Watergate scandal, of “making up stories”. Trump was perhaps referring to a CNN story that his former attorney Michael Cohen claimed the US president knew in advance about a June 2016 meeting with Russians, who were to provide information on Hillary Clinton, his opponent in that year’s presidential election. Bernstein co-wrote the story.