WASHINGTON (NYTIMES) - United States President Donald Trump told his national security adviser in August 2019 that he wanted to continue freezing US$391 million (S$529 million) in security assistance to Ukraine until officials there helped with investigations into Democrats including the Bidens, according to an unpublished manuscript by the former adviser, John Bolton.

The president's statement as described by Bolton could undercut a key element of his impeachment defence: that the holdup in aid was separate from Trump's requests that Ukraine announce investigations into his perceived enemies, including former Vice President Joe Biden and his son Hunter Biden, who had worked for a Ukrainian energy firm while his father was in office.

Bolton's explosive account of the matter at the centre of Trump's impeachment trial, the third in American history, was included in drafts of a manuscript he has circulated in recent weeks to close associates.

He also sent a draft to the White House for a standard review process for some current and former administration officials who write books.

Multiple people described Bolton's account of the Ukraine affair.

The book presents an outline of what Bolton might testify to if he is called as a witness in the Senate impeachment trial, the people said. The White House could use the pre-publication review process, which has no set time frame, to delay or even kill the book's publication or omit key passages.

Over dozens of pages, Bolton described how the Ukraine affair unfolded over several months until he departed the White House in September. He described not only the president's private disparagement of Ukraine but also new details about senior Cabinet officials who have publicly tried to sidestep involvement.

For example, Secretary of State Mike Pompeo acknowledged privately that there was no basis to claims by the president's lawyer Rudy Giuliani that the ambassador to Ukraine was corrupt and believed Giuliani may have been acting on behalf of other clients, Bolton wrote.

Bolton also said that after the president's July phone call with the president of Ukraine, he raised with Attorney General William Barr his concerns about Giuliani, who was pursuing a shadow Ukraine policy encouraged by the president, and told Barr that the president had mentioned him on the call. A spokesman for Barr denied that he learned of the call from Bolton; the Justice Department has said he learned about it only in mid-August.

And the acting White House chief of staff, Mick Mulvaney, was present for at least one phone call where the president and Giuliani discussed the ambassador, Bolton wrote. Mulvaney has told associates he would always step away when the president spoke with his lawyer to protect their attorney-client privilege.

During a previously reported May 23 meeting where top advisers and Republican Senator Ron Johnson, briefed him about their trip to Kiev for the inauguration of President Volodymyr Zelenskiy, Trump railed about Ukraine trying to damage him and mentioned a conspiracy theory about a hacked Democratic server, according to Bolton.

The White House did not provide responses to questions about Bolton's assertions, and representatives for Johnson, Pompeo and Mulvaney did not respond to emails and calls seeking comment Sunday afternoon.

Bolton's lawyer blamed the White House for the disclosure of the book's contents. "It is clear, regrettably, from the New York Times article published today that the pre-publication review process has been corrupted and that information has been disclosed by persons other than those properly involved in reviewing the manuscript," the lawyer, Charles J. Cooper, said Sunday night.

He said he provided a copy of the book to the White House on Dec. 30 - 12 days after Trump was impeached - to be reviewed for classified information, though, he said, Bolton believed it contained none.

The submission to the White House may have given Trump's aides and lawyers direct insight into what Bolton would say if he were called to testify at Trump's impeachment trial. It also intensified concerns among some of his advisers that they needed to block Bolton from testifying, according to two people familiar with their concerns.

The White House has ordered Bolton and other key officials with firsthand knowledge of Trump's dealings not to cooperate with the impeachment inquiry. Bolton said in a statement this month that he would testify if subpoenaed.

In recent days, some White House officials have described Bolton as a disgruntled former employee, and have said he took notes that he should have left behind when he departed the administration.

Trump told reporters last week that he did not want Bolton to testify and said that even if he simply spoke out publicly, he could damage national security.

"The problem with John is it's a national security problem," Trump said at a news conference in Davos, Switzerland. "He knows some of my thoughts. He knows what I think about leaders. What happens if he reveals what I think about a certain leader and it's not very positive?" "It's going to make the job very hard," he added.

Bolton, 71, a fixture in conservative national security circles since his days in the Reagan administration, joined the White House in 2018 after several people recommended him to the president, including the Republican mega-donor Sheldon Adelson.

But Bolton and Trump soured on each other over several global crises, including Iranian aggression, Trump's posture toward Russia and, ultimately, the Ukraine matter. Bolton was also often at odds with Pompeo and Mulvaney throughout his time in the administration.

Key to Bolton's account about Ukraine is an exchange during a meeting in August with the president after Trump returned from vacation at his golf club in Bedminster, New Jersey. Bolton raised the US$391 million in congressionally appropriated assistance to Ukraine for its war in the country's east against Russian-backed separatists. Officials had frozen the aid, and a deadline was looming to begin sending it to Kyiv, Bolton noted.

He, Pompeo and Defence Secretary Mark T. Esper had collectively pressed the president about releasing the aid nearly a dozen times in the preceding weeks after lower-level officials who worked on Ukraine issues began complaining about the holdup, Bolton wrote. Trump had effectively rebuffed them, airing his long-standing grievances about Ukraine, which mixed legitimate efforts by some Ukrainians to back his Democratic 2016 opponent, Hillary Clinton, with unsupported accusations and outright conspiracy theories about the country, a key American ally.

Giuliani had also spent months stoking the president's paranoia about the US ambassador to Ukraine at the time, Marie L. Yovanovitch, claiming that she was openly anti-Trump and needed to be dismissed. Trump had ordered her removed as early as April 2018 during a private dinner with two Giuliani associates and others, a recording of the conversation made public Saturday showed.

In his August 2019 discussion with Bolton, the president appeared focused on the theories Giuliani had shared with him, replying to Bolton's question that he preferred sending no assistance to Ukraine until officials had turned over all materials they had about the Russia investigation that related Biden and supporters of Clinton in Ukraine.

The president often hits at multiple opponents in his harangues, and he frequently lumps together the law enforcement officials who conducted the Russia inquiry with Democrats and other perceived enemies, as he appeared to do in speaking to Bolton.