Updated at 1:20 a.m. ET
Democrats are pressing the Senate to call former national security adviser John Bolton to testify in President Trump's impeachment trial following a new report that House impeachment managers describe as "explosive."
The New York Times reported Sunday evening that Bolton wrote in a forthcoming book that the president told him in August he wanted to continue withholding close to $400 million in military assistance to Ukraine until that country's government agreed to launch investigations of former Vice President Joe Biden and his son Hunter.
The Times report cited accounts from multiple unnamed sources who said they had seen drafts of a manuscript from Bolton's book about his time in the White House. NPR has not seen a draft of the manuscript and cannot vouch for the accuracy of the report.
Bolton's lawyer, Charles Cooper, said in an emailed statement to NPR that he had submitted a copy of the manuscript to the National Security Council on Dec. 30 to ensure that no classified information was disclosed. Cooper said his understanding was that the manuscript would not be disclosed to officials not regularly involved in the review process.
"It is clear, regrettably, from The New York Times article published today that the prepublication review process has been corrupted and that information has been disclosed by persons other than those properly involved in reviewing the manuscript," Cooper said.
In a post-midnight tweet, Trump denied the account.
"I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens," he wrote. "If John Bolton said this, it was only to sell a book."
The Times' report landed as Trump's defense team prepares to argue against the president's removal in his Senate impeachment trial on Monday.
Democratic House impeachment managers argue that the story bolsters their argument to have the Senate call Bolton as a witness at the trial, and to provide his notes and documents.
"The Senate trial must seek the full truth and Mr. Bolton has vital information to provide," the House impeachment team said in a statement. "Americans know that a fair trial must include both the documents and witnesses blocked by the President — that starts with Mr. Bolton."
Other senior Democrats backed the House impeachment managers' demand.
"John Bolton has the evidence," Senate Minority Leader Chuck Schumer, D-N.Y., tweeted. "It's up to four Senate Republicans to ensure that John Bolton, Mick Mulvaney, and the others with direct knowledge of President Trump's actions testify in the Senate trial."
House Speaker Nancy Pelosi, D-Calif., said in a tweet that the Times report provides Republican senators with a choice between "our Constitution or a cover-up."
The House impeachment inquiry had asked Bolton to testify, but did not issue him a subpoena. Although the White House had ordered senior officials not to testify, Bolton said earlier this month that he would comply if the Senate issued a subpoena for his testimony.
Bolton and his deputy Charles Kupperman had wanted a federal court to rule on whether they should follow the House request or the White House order, but the House withdrew a subpoena for Kupperman and did not pursue the matter in court.
The White House and National Security Council did not respond to requests for comment from NPR.