Journalist Bob Woodward alleges in his upcoming book Fear that President Donald Trump demanded last year that Syrian President Bashar al-Assad be assassinated.

The claim was reported Tuesday after excerpts of the veteran reporter’s new book were published by the Washington Post. Fear is set to be released on September 11.

Woodward — who along with Carl Bernstein is best known for breaking the Watergate scandal that engulfed President Richard Nixon in the 1970s — claims Defense Secretary James Mattis ignored Trump’s order to kill Assad. The book asserts Trump was infuriated that the Syrian leader had launched a chemical weapons attack against his own people in April 2017.

“Let’s f—ing kill him!” Trump reportedly told top administration officials last year. “Let’s go in. Let’s kill the f—ing lot of them.”

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Mattis eventually devised a plan to launch a limited air strike against the Syrian government. Woodward also claims the defense secretary said Trump acted like and had the understanding “of a fifth grader or sixth grader” with regard to international affairs like negotiating denuclearization with North Korea. Mattis also says in his new book that chief of staff John Kelly reportedly referred to the White House as “crazytown.”

Trump was famously criticized by many top intelligence officials and lawmakers — like late Sen. John McCain, a former Navy veteran and chairman of the Senate Armed Services Committee — because of his brash response to the crisis in Syria.

Woodward also alleges in Fear that Trump has repeatedly insulted dozens of other administration officials, like Attorney General Jeff Sessions. 

“This book is nothing more than fabricated stories, many by former disgruntled employees, told to make the President look bad,” the White House said in a statement on Tuesday.