The author of an explosive book on US President Donald Trump stands by everything he has written.
Mr Trump is rejecting claims in Fire and Fury: Inside the Trump White House that the White House is in chaos and he is unstable.
Author Michael Wolff told NBC News many working for the President don't think Mr Trump is up to the job.
"Let me put a marker in the sand here - 100 percent of the people around him...
they all say is he is like a child. And what they mean by that is he has a need for immediate gratification. It's all about him... He just has to be satisfied in the moment."
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Mr Trump has accused Mr Wolff of fabricating the "phony book", saying he never authorised any access for the author, nor spoke to him. Mr Wolff said Mr Trump is wrong.
"What was I doing there if he didn't want me to be there? I absolutely spoke to the President. Whether he realised it was an interview or not, I don't know. But it certainly was not off the record."
In a tweet on Friday (NZ time), Mr Trump said the book was "full of lies, misrepresentations and sources that don't exist".
Despite this, or perhaps because of it, Fire and Fury is flying off the shelves. A bookstore in Washington DC which opened at midnight to be the first to sell it sold out of copies inside of 20 minutes, according to Buzzfeed News reporter Chris Geidner.
It's also rocketed straight to the top of Amazon's bestseller chart.
Among the book's claims:
- Former strategist Steve Bannon called the President's connections to Russia "treasonous and unpatriotic".
- MrTrump bragged that sleeping with his friends' wives "made life worth living".
- Ivanka Trump aims to be the first female President.
- Mr Trump retreats to his bedroom with a cheeseburger at 6:30pm to watch TV.
- While he admires media mogul Rupert Murdoch, Mr Murdoch has called Mr Trump a 'f***ing idiot'.
- Mr Trump has difficulty recognising old friends and repeats himself constantly, causing multiple close aides to describe him as "incapable of functioning in his job".
Mr Wolff says he has proof everything he's written in true.
"I work like every journalist works. I have recordings, I have notes. I am certainly and absolutely, in every way, comfortable with everything I've reported in this book."
The book's contents have sparked open questioning of Mr Trump's mental fitness to lead, which White House spokeswoman Sarah Huckabee Sanders has blasted as "disgraceful".
The Trump administration has tried to get publication of the book stopped, but it appears to be too late.