Donald Trump has been described as "unhinged", an "idiot" and has the understanding of a "fifth-grader", according to White House sources cited in a new book.
The US President has been depicted as angry and paranoid in the book Fear by Washington Post associate editor Bob Woodward, the reporter known for helping uncover the Watergate scandal that brought down former US President Richard Nixon.
Mr Woodward claims to have interviewed a range of White House top aides, including Mr Trump's chief of staff, John Kelly. It is alleged Mr Kelly called his boss an "idiot" and said it's "pointless to try to convince him of anything".
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"He's gone off the rails. We're in Crazytown. I don't even know why any of us are here. This is the worst job I've ever had," Mr Kelly is quoted saying in the book, which the Washington Post says it obtained before its release.
The author said he reached out to Mr Trump for an interview, but to no avail. However, the President contacted him in early August asking to participate.
In an audio recording published online by the Washington Post, Mr Trump is heard saying it would be a "bad book", to which Mr Woodward retorted it would be "tough" but factual.
The book also details Mr Trump's apparent paranoia regarding the Russia investigation led by special counsel Robert Mueller into alleged collusion. The President is said to have called the investigation "a goddamn hoax", adding that he doesn't want to testify.
Mr Trump's fury over chemical weapons being used in Syria is also detailed in the book. He's quoted telling US defence secretary Jim Mattis about Syrian President Bashar Al-Assad: "Let's f***ing kill him! Let's go in. Let's kill the f***ing lot of them!"
Mr Mattis, who is alleged to have described Mr Trump as having the understanding of a "fifth-grader", tells his boss, "We're not going to do any of that. We're going to be much more measured," after Mr Trump's outburst over Syria.
The revelations come after former White House aide Omarosa Manigault Newman made damning claims about Preisdent Trump in her soon-to-be released book Unhinged: An Insider Account of the Trump White House.
Ms Newman has known Mr Trump for over a decade, including working with him during his show The Apprentice, where she said a tape was made of him using the N-word.