Former national security adviser John Bolton said he will not vote for President Donald Trump in the upcoming election, just days before the release of whats expected to be a scathing tell-all about his tenure in the White House.

I dont think hes a conservative Republican. Im not going to vote for him in November certainly not going to vote for Joe Biden either, Bolton told ABC News Martha Raddatz in an interview that aired Sunday. Im going to figure out a conservative Republican to vote in.

He continued: I think the concern I have speaking as a conservative Republican is that once the election is over, if the president wins, the political constraint is gone. And because he has no philosophical grounding, theres no telling what will happen in a second term.

The appraisal is an extraordinary rebuke of a sitting president by a high-ranking former aide. Bolton cast Trump as a danger for the Republic and said he was erratic and impulsive.

The comments came shortly after the Daily Telegraph reported the former aide had no plans to see Trump return to the White House, saying the man does not represent the Republican cause that I want to back. (The outlet initially reported Bolton would cast a ballot for presumptive Democratic nominee Joe Biden, but a spokesman later said that was false .)

The president does not have a philosophical grounding or strategy, Bolton told the British outlet. He does not know the difference between the national interest of the U.S., and the interests of Donald Trump. There is confusion over the national interest and his personal interest, which is very dangerous for the country.

The declarations come just days before Boltons book, The Room Where It Happened, will be published. The memoir reportedly includes bombshells that Trump asked Chinese President Xi Jinping to help him win reelection in 2020 and also urged Xi to build facilities akin to concentration camps to hold Uighur Muslims.

Trump has raged against his former aide , calling him a liar, a dope and a sick puppy, and his administration has moved to block the books publication. A judge rejected the White Houses request to do so last week, noting hundreds of thousands of copies had already been shipped.

Bolton resigned last September , although Trump has maintained that he was fired. The pair reportedly clashed over foreign policy decisions in Iran and North Korea.