A tweet drafted by President Donald Trump ― but never posted ― had the potential to lead to war with North Korea, veteran journalist Bob Woodward said on Sunday.

“He drafts a tweet saying ‘We are going to pull out dependents from South Korea ... Family members of the 28,000 people there,’” Woodward said on CBS “Sunday Morning” as he promoted his upcoming book, Fear: Trump in the White House.

But a backchannel message from North Korea said bringing family members home would be considered a sign of an impending U.S. attack.

“At that moment there was a sense of profound alarm in the Pentagon leadership that, ‘My God, one tweet and we have reliable information that the North Koreans are going to read this as an attack is imminent,’” Woodward said.

An excerpt of the book obtained by The Atlantic said the nearly-posted tweet “scared the daylights” out of Defense Secretary Jim Mattis﻿ and Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford.

At the time, Trump and North Korean President Kim Jong Un routinely traded threats and insults. Trump derided Kim as “Little Rocket Man” and bragged about having a “much bigger & more powerful” nuclear button. Kim, for his part, denounced Trump as a “dotard.”

However, a summit between the two in Singapore earlier this year eased tensions, and over the weekend Trump even thanked the North Korean dictator for not showing off nuclear missiles during a military parade in Pyongyang.

Fear hits bookstores on Tuesday. Trump said the book was “already discredited” and has “so many lies and phony sources.”