Trump's White House depicted as 'Crazytown' in new book

President Donald Trump's White House is mired in a perpetual "nervous breakdown" with staff battling to rein in the worst impulses of an angry, paranoid leader, according to an explosive new book by veteran reporter Bob Woodward.

Drawing on hundreds of hours of interviews, Woodward describes a coalition of like-minded aides plotting to prevent the US president from destroying the world trade system, undermining national security and sparking wars.

While Woodward's is not the first unflattering book into Trump's White House, it carries particular weight coming from the man who together with Carl Bernstein authored the Watergate expose that brought down Richard Nixon.

Trump's White House is described as having undergone "no less than an administrative coup d'etat," according to The Washington Post where Woodward is an associate editor and which received an advance copy of the 448-page book entitled Fear: Trump in the White House, set for release on September 11.

The White House hit back at "fabricated stories" as the long-awaited book piled fresh pressure on a president besieged by multiple investigations and a looming election that could damage his Republican Party.

Trump claimed that the quotes in Woodward's book were "made up frauds, a con on the public. Likewise other stories and quotes."

"Woodward is a Dem operative? Notice timing?" he added, after tweeting earlier statements by Defence Secretary James Mattis, White House Chief of Staff John Kelly and spokeswoman Sarah Sanders refuting the quoted statements as false.

Mattis and former economic adviser Gary Cohn are cited among the aides actively circumventing Trump's orders and even stealing documents off his desk.

Woodward recounts that Mattis -- having had to explain to the president that the US must keep forces in South Korea "to prevent World War III" -- told colleagues that Trump had the understanding of "a fifth- or sixth-grader," a 10- or 11-year-old child.

After the April 2017 chemical attack blamed on Bashar al-Assad, Woodward claims Trump called the Pentagon chief to press for the Syrian leader's assassination.

"Let's f#*king kill him! Let's go in. Let's kill the f#*king lot of them," Trump reportedly told him. Mattis agreed to take action -- but after hanging up ordered "more measured" steps against Syria, a punitive air strike.

Mattis was among several high-profile figures quoted by Woodward who issued swift denials.

"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, charging that the journalist's "anonymous sources do not lend credibility."

While he does not name his sources, Woodward says he spoke with many people currently or formerly working for Trump as he researched the book, discussing not just the president's personality but also major policy debates regarding North Korea and Afghanistan.

Woodward describes Trump regularly insulting key members of his own team, branding Attorney General Jeff Sessions "mentally retarded" and a "dumb Southerner," and saying former chief of staff Reince Priebus is "like a little rat."

Trump is quoted as telling his hand-picked 80-year-old secretary of commerce, Wilbur Ross, "I don't trust you... You're past your prime."

The aides and cabinet members respond, privately, with equal disdain.

According to Woodward, Kelly told colleagues Trump is "unhinged" and "an idiot." "It's pointless to try to convince him of anything. He's gone off the rails. We're in Crazytown," Kelly is quoted as saying.

Former Trump lawyer John Dowd called Trump "a f#*king liar," the book says.

Both Kelly and Dowd denied the quotes attributed to them -- although Woodward is not the first to cite them making brutal comments about the president.

Since the Watergate expose appeared in The Washington Post in the early 1970s, Woodward has published powerful, insightful and often embarrassing books on eight US leaders, including George W Bush and Barack Obama, based on extensive access to many White House insiders.

Woodward is one of the most respected living US journalists, and an authority on modern US presidents who drew praise from Trump himself in 2013 for his work on Obama. Fear is flecked with accounts of White House officials working to prevent Trump's anger and paranoia from being translated into policy.