Woodward told CBS that President Donald Trump was fixated on the US's spending $3.5 billion a year to station troops in South Korea and that Trump once drafted a tweet appearing to signal to North Korea the US's willingness to to go to war.

President Donald Trump nearly provoked North Korea into war with a single tweet, the renowned journalist Bob Woodward said in an interview with CBS that aired Sunday.

Woodward discussed his new book, "Fear: Trump in the White House," and said Trump was fixated on the US's spending $3.5 billion a year to station 28,000 troops in South Korea.

Woodward said Trump once drafted a tweet calling to remove the families of those troops stationed in South Korea.

The tweet was never sent out, reportedly because of back-channel communications with North Korea that indicated the North would regard the move as a sign the US was preparing to wage war.

President Donald Trump nearly provoked North Korea into war with a single tweet, the renowned journalist Bob Woodward said in an interview with "CBS Sunday Morning" that aired Sunday.

In the interview, Woodward discussed his new book, "Fear: Trump in the White House," and said Trump was fixated on the US's spending $3.5 billion a year to station troops in South Korea.

"I don't know why they're there," Trump told top officials during a meeting, according to Woodward's explosive new book. "Let's get them out."

Secretary of Defense James Mattis told Trump in another meeting that troops were there to "prevent World War III," the book says.

Trump had a series of contentious public exchanges with North Korea last year. In October, Trump tweeted that his secretary of state at the time, Rex Tillerson, was "wasting his time trying to negotiate with Little Rocket Man," a nickname for North Korean leader Kim Jong Un. According to Woodward's book, Trump told Rob Porter, then a staff secretary, that the tweet "may be my best ever."

According to Woodward, Porter asked the president whether the tweet might provoke Kim, to which Trump reportedly replied: "It's leader versus leader. Man versus man. Me versus Kim."

Woodward told CBS the most "dangerous" moment of Trump's standoff with Kim came when the president went to produce another provocative tweet.

"He drafts a tweet saying, 'We are going to pull our dependents from South Korea — family members of the 28,000 people there,'" Woodward told CBS.

According to Woodward, the tweet was never sent out after back-channel communications with North Korea made clear that the nation would regard the move as a sign the US was preparing to wage war on the North.

"In 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.

Woodward told CBS that Trump's staffers were concerned that the president could make an impulsive decision that could have major global consequences.

"People who work for him are worried that he will sign things or give orders that threaten the national security or the financial security of the country or the world," Woodward said.

Relations with North Korea are on edge

Kevin Lim/THE STRAITS TIMES/Handout/Getty Images

Relations between Trump and Kim thawed this year but have grown stale since their summit in June, where the two parties pledged to move toward denuclearizing the Korean Peninsula.

Last month, Trump canceled Secretary of State Mike Pompeo's trip to North Korea, reportedly after the country sent out a mysterious letter, pointing to potential hostilities between the two leaders.

North Korea has upped its rhetoric against the US in recent months, and North Korea's state newspaper accused Washington of plotting to "unleash a war" on Pyongyang while continuing to negotiate "with a smile on its face."

Kim told China's state broadcaster Sunday that North Korea was keeping up with its end of the agreement it reached in June and hoped the US kept its side of the deal.