US President Donald Trump's former national security advisor, John Bolton, has accused him of seeking China's help to win re-election.
The Trump administration is seeking an injunction to block publication of a book by Mr Bolton that is due out next week.
Extracts that have appeared in US newspapers claim that President Trump asked Chinese President Xi Jinping to help him win a second term in office by buying agricultural goods from politically important farming states hit by the trade dispute between the two countries.
The claim has been denied by the Trump administration.
Mr Bolton, who was fired by Mr Trump in September over policy differences, also said that the president had expressed a willingness to halt criminal investigations to give "personal favours to dictators he liked," according to a book excerpt published in the New York Times ahead of its release.
President Trump hit back at Mr Bolton, calling him "a liar" in an interview with the Wall Street Journal.
The paper also published excerpts of the book, titled "The Room Where It Happened: A White House Memoir," as did the Washington Post.
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President Trump told Fox News in a separate interview that Mr Bolton had broken the law by including highly classified material in the book.
Together, the excerpts portray a US President mocked by his top advisers who exposed himself to far more extensive accusations of impropriety than those that drove the Democratic-led House of Representatives to impeach Mr Trump last year.
The Republican-led Senate acquitted the president in early February.
Mr Trump was accused of withholding US military aid last year to put pressure on newly-elected Ukrainian President Volodymr Zelensky to provide damaging information on Democratic political opponent Joe Biden.
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"Had Democratic impeachment advocates not been so obsessed with their Ukraine blitzkrieg in 2019, had they taken the time to inquire more systematically about President Trump's behaviour across his entire foreign policy, the impeachment outcome might well have been different," Mr Bolton wrote, according to excerpts in the Wall Street Journal.
Critics of Mr Bolton note he declined to testify before the House of Representatives inquiry when his disclosures could have been critical.
Representative Adam Schiff, the California Democrat who led the prosecution of President Trump, a Republican, slammed Mr Bolton for saying at the time that "he'd sue if subpoenaed".
"Instead, he saved it for a book," Mr Schiff said on Twitter. "Bolton may be an author, but he's no patriot."
Still, Mr Bolton's allegations provide new ammunition to critics ahead of 3 November presidential election, including his behind-the-scenes accounts of President Trump's conversations with Mr Xi, which, in one case, broached the topic of the US vote.
"Trump then, stunningly, turned the conversation to the coming US presidential election, alluding to China's economic capability and pleading with Mr Xi to ensure he'd win," Mr Bolton wrote, in the most in-depth, damaging portrayal by a Trump administration insider to date and just days after former defence secretary Jim Mattis accused the president of trying to divide America.
Mr Biden said in a statement: "If these accounts are true, it's not only morally repugnant, it’s a violation of Donald Trump’s sacred duty to the American people."
US trade representative Robert Lighthizer said in Senate testimony that Mr Bolton's account was "absolutely untrue".
"I was at the meeting. Would I recollect something as crazy as that? Of course I would," Mr Lighthizer said. "This never happened in it for sure. Completely crazy."
The US government has sued to block Mr Bolton from publishing the book, citing risks to national security, and is seeking a court hearing tomorrow.
Publisher Simon & Schuster has dismissed the accusations and said "hundreds of thousands of copies" of the book have already been distributed.
Although the Trump administration had been strongly critical of China's mass detention of mostly Muslim Uighur minority and other Muslim groups, Mr Trump gave Mr Xi a green light in June 2019 in Osaka, Japan, Mr Bolton said.
"According to our interpreter, President Trump said that Mr Xi should go ahead with building the camps, which Mr Trump thought was exactly the right thing to do," Mr Bolton wrote, adding that another top White House official said the president made similar comments during his November 2017 trip to China.
Mr Bolton cited an innumerable number of conversations in which President Trump demonstrated "fundamentally unacceptable behaviour that eroded the very legitimacy of the presidency".
A former US ambassador to the United Nations and Fox News television commentator, Mr Bolton's hawkish approach had worn on a president weary of foreign military entanglements, officials say.
President Trump would sometimes chide Mr Bolton in meetings, introducing him to visiting foreign leaders by saying: "You all know the great John Bolton. He’ll bomb you. He’ll take out your whole country."
In excerpts published in the Washington Post, Mr Bolton writes that Mr Trump said invading Venezuela would be "cool" and that it was "really part of the United States".
The US government has publicly said it does not favour using force to topple Venezuela's socialist President Nicolas Maduro.
The book also exposed the sometimes dim view that President Trump's advisers have of him.
During a 2018 meeting with North Korean leader Kim Jong Un, Mr Bolton says he got a note from Secretary of State Mike Pompeo mocking Mr Trump, according to an excerpt in the Washington Post.
Although Mr Trump is publicly critical of journalists, Mr Bolton's book quotes the president making some of his most alarming remarks to date.
In a summer 2019 meeting in New Jersey, President Trump allegedly said journalists should be jailed so they have to divulge their sources: "These people should be executed. They are scumbags," according to another excerpt in the Washington Post.
Mr Trump is also said to have ignored basic facts such as Finland being a distinct country from Russia.
Bolton book says Trump did not know UK was nuclear power
Mr Trump was unaware the UK was a nuclear power and came closer to withdrawing the United States from NATO than is widely believed, according to leaks from Mr Bolton's book, saying the president is "stunningly uninformed".
One excerpt told of a 2018 meeting with then British prime minister Theresa May in which a UK official referred to Britain as a nuclear power.
Mr Trump is said to have replied: "Oh, are you a nuclear power?"
Mr Bolton makes it clear the line was not intended as a joke.
The former ambassador also wrote that at a NATO summit in 2018 President Trump had decided to tell allies the US would pull out of the group if other countries did not increase their defence spending, telling Mr Bolton in a message: "We will walk out, and not defend those who have not (paid)."
Mr Trump, however, ultimately did not make such a dramatic threat, with the US staying in the alliance.
Mr Bolton said the president had on occasion expressed a willingness to stop criminal investigations involving companies in China and Turkey in order to "give personal favours to dictators he liked".
Additional reporting PA
