WASHINGTON (BLOOMBERG) - Donald Trump isn't "fit for office" and lacks the "competence" to serve as president in part because he's solely focused on his political fortunes, former national security adviser John Bolton said.

Bolton's comments in an interview with ABC News come as he is promoting his tell-all memoir, which delivers withering criticism of Trump's leadership from one of his former top advisers.

The president has attempted to discredit Bolton, tweeting early on Thursday (June 18) that his book is "made up of lies & fake stories."

"I don't think he's fit for office. I don't think he has the competence to carry out the job," Bolton said of Trump in a portion of the ABC interview that aired on Thursday.

Bolton's memoir, entitled The Room Where It Happened, paints Trump as woefully uninformed and describes a series of troubling encounters with foreign leaders, which Bolton said proved the president was consumed with his political standing above all else.

The former top security aide alleges that Trump asked Chinese President Xi Jinping to help him win re-election by buying more US farm products, one of many examples that Bolton says the House could have investigated in its impeachment probe.

"There really isn't any guiding principle that I was able to discern other than what's good for Donald Trump's re-election," Bolton said.

"He was so focused on the re-election that longer-term considerations fell by the wayside."

The book is poised to further hamper Trump's re-election campaign, which has already been hurt by the president's handling of mass demonstrations against police brutality and the coronavirus pandemic.

'BROKE THE LAW'

Trump mounted his defence late on Wednesday, accusing Bolton of breaking the law by trying to publish the book, which the president said contains classified information. Earlier in the day, the Justice Department sought an emergency restraining order to block its publication, scheduled for June 23.

"He broke the law, very simple. As much as it's going to be broken," Trump told Fox News host Sean Hannity in an interview on Wednesday night. "This is highly classified."

In a separate interview on Wednesday with the Wall Street Journal, Trump defended his handling of China and other nations while dismissing several of Bolton's allegations as coming from a "crazy" person and a "liar."

Trump referred to Bolton as a "wacko" in his Thursday tweet, and argued the book is contradicted by his past praise for Trump.

"Said all good about me, in print, until the day I fired him. A disgruntled boring fool who only wanted to go to war. Never had a clue, was ostracized & happily dumped. What a dope!" the president tweeted.

He called the book "a compilation of lies and made up stories."

Bolton writes that Trump gave Xi his blessing during last year's Group of 20 summit to China's detention camps for Uighur Muslims, an example of how the former national security adviser said the president valued a trade deal with China at the expense of human rights and the US' national interest.

"That's not true," Trump said of Bolton's description of his conversation with Xi in the Journal interview.

Trump pointed out that he signed legislation on Wednesday that could lead to sanctions against China over the camps.

The signing was announced soon after excerpts of Bolton's book were published by news outlets on Wednesday.

"I could have killed that very easily," Trump said of the measure.

HUAWEI, ZTE

But the president did not deny Bolton's claim that he wanted to lift penalties on major Chinese companies in order to curry favor with Xi during talks over the phase one trade agreement.

Bolton writes that he and other advisers persuaded Trump to reimpose a ban on Huawei Technologies from doing business with US companies, after Trump offered to reverse criminal prosecutions against the company.

"Nobody has ever been so tough on a company as I have to Huawei," Trump said.

Trump also said ZTE Corp. was hit with a US$1.3 billion (S$1.8 billion) penalty as well as changes to its board, even though he pulled back on harsher punishments over allegations it violated US sanctions on Iran and North Korea.

"ZTE was my deal," Trump said. "It was an unbelievable deal."

Bolton also said many of Trump's top advisers viewed the president with disdain, including Michael Pompeo, whom Bolton said considered resigning as secretary of state. Bolton writes that during one meeting, Pompeo passed him a note that said of the president: "he is so full of s***," according to the Journal.

NORTH KOREA PHOTO-OP

Trump said he has a "very good relationship" with Pompeo and disputed Bolton's account.

"I would doubt that," Trump told the Journal. "Does he have the note? Let me see the note."

Bolton said Trump's desire to place his personal interests ahead of the country's extended to his dealings with other world leaders, including North Korea's Kim Jong Un.

A longtime North Korea hawk, Bolton hammered Trump over his decision to meet Kim last June in the Korean demilitarised zone before Pyongyang had taken significant steps to dismantle its nuclear programme.

"So if he thought he could get a photo opportunity with Kim Jong Un in the demilitarised zone in Korea, there was considerable emphasis on the photo opportunity and the press reaction to it and little or no focus on what such meetings did for the bargaining position of the United States," Bolton told ABC.

Trump shot back by accusing Bolton of hurting his relationship with Kim by saying in 2018 that North Korea's disarmament should follow the "Libya model." Libyan leader Moammar Qaddafi was overthrown and killed in a US-backed uprising years after agreeing to surrender his nuclear weapons.

"I should have fired him right then & there!" Trump tweeted.