The White House is claiming that “significant amounts of classified information” in John Bolton’s new book must be removed before it can be published.
A letter from the National Security Council (NSC) to Mr Bolton’s lawyer, Charles Cooper, said some of the material in the manuscript was believed to be top secret and needs to be deleted before it can hit the shops.
Donald Trump’s ex-national security adviser wrote in the manuscript that the president told him he wanted to freeze $391m (£300m) in security aid to Ukraine until Kiev investigated Democratic political rival Joe Biden and his son Hunter, according to The New York Times.
The reported conversation between Mr Trump and Mr Bolton contradicts the Republican president’s defence in his current impeachment trial.
Democrats see Mr Bolton as a key figure who could help them with their case against the president and they want to call Mr Bolton and several other officials to testify in the Senate trial.
But many Republicans have so far objected to having any witnesses and Mr Trump has dismissed the charges brought by Democrats in the House of Representatives as a “hoax” and a “witch-hunt”.
He and his allies have said the hold on military aid and investigations were not linked, and the president has said he “never” had such a conversation with Mr Bolton.
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Mr Cooper submitted Mr Bolton’s manuscript to the NSC last month for a routine security review “notwithstanding our firm belief that the manuscript contained no information that could reasonably be considered classified”.
But in the letter to Mr Cooper, dated 23 January, a NSC aide wrote: “Based on our preliminary review, the manuscript appears to contain significant amounts of classified information. It also appears that some of this classified information is at the top-secret level.”
Ellen Knight, NSC senior director for records, access and information security management, added: “The manuscript may not be published or otherwise disclosed without the deletion of this classified information.”
The US leader is accused of putting pressure on Ukrainian President Volodymyr Zelenskiy to investigate White House hopeful Mr Biden by threatening to withhold military assistance.
Democrats claim Mr Trump abused his power by pressuring Kiev to help him politically, and obstructed Congress when it tried to find out what happened.
On Wednesday, the president tweeted: “Why didn’t John Bolton complain about this ‘nonsense’ a long time ago, when he was very publicly terminated. He said, not that it matters, NOTHING!”
He also wrote: “No matter how many witnesses you give the Democrats, no matter how much information is given, like the quickly produced Transcripts, it will NEVER be enough for them. They will always scream UNFAIR. The Impeachment Hoax is just another political CON JOB!”
On Monday, Mr Trump tweeted: “I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens. In fact, he never complained about this at the time of his very public termination. If John Bolton said this, it was only to sell a book.”
“With that being said, the transcripts of my calls with President Zelenskiy are all the proof that is needed, in addition to the fact that President Zelenskiy & the Foreign Minister of Ukraine said there was no pressure and no problems.”
The impeachment vote in the Republican-dominated Senate is expected to be mostly along party lines and it is therefore unlikely Mr Trump will be removed from office.