The lawyer for former National Security Advisor John Bolton is pushing back on White House claims that his forthcoming book has a bunch of top-secret, classified material in it, and wants the White House’s review expedited as President Donald Trump’s impeachment trial churns on.

Bolton’s attorney, Charles Cooper, sent an email to NSC officials on Jan. 24 in response to a letter sent by National Security Council officials a day earlier about the contents of the book, according to the Washington Post. “We do not believe that any of that information could reasonably be considered classified,” Cooper wrote.

Cooper also added that it was “imperative that we have the results of your review of that chapter as soon as possible,” given the possibility Bolton could be called to testify in Trump’s impeachment trial, according to the Post. Cooper has yet to receive a response, he told the Post in a statement.

The release of the letter comes after Trump tweeted Wednesday that Bolton’s book, which he called “nasty and untrue,” was “All Classified National Security. Who would do this?”

Cooper sent the manuscript to the White House for review on December 30, according to a letter originally obtained by the New York Times. In the NSC’s response, dated Jan. 23, senior director for records Ellen Knight told Cooper that Bolton would be breaking his nondisclosure agreement if the book were published in its current form, according to the Post.

On Sunday, two days after Cooper responded to the NSC, details from the manuscript were published in the New York Times, including an account of a conversation Bolton allegedly had with Trump where the president told him he wanted to continue to freeze military aid to Ukraine until the country began investigating Trump's political rival Joe Biden and his son Hunter.

The following day, the Times published more from the manuscript, namely details of a conversation between Bolton and Attorney General William Barr worrying about Trump’s relationship with Turkish President Recep Erdoğan and Chinese leader Xi Jinping. (The Justice Department has denied Bolton’s account of this conversation.)

It’s unclear yet whether enough Senate Republicans will join with Democrats to call Bolton to testify. On Wednesday night, GOP Sen. Ted Cruz told reporters that if they did decide to call Bolton, they’ll also call Hunter Biden to testify.