Trump reportedly called North Korean leader Kim Jong Un a 'lunatic': book

• Former President Donald Trump called Kim Jong Un "a fucking lunatic," according to a new book.
• The comment was reportedly made in the presence of Lt. Gen. Keith Kellogg, a staunch ally of Trump.
• While Trump and Kim managed to mend fences, their earlier exchanges featured a furious war of words.

Despite the public show of affection between former President Donald Trump and North Korean dictator Kim Jong Un as they sought to propel the denuclearization of the Korean Peninsula, the former president made a less-than-flattering comment about the leader during his time in office, according to an upcoming book by Washington Post journalists Bob Woodward and Robert Costa.

Insider obtained an early copy of the book, "Peril," which at one point details the relationship between Trump and Ret. Lt. Gen. Keith Kellogg, a staunch ally of the then-president who also worked as the national security advisor for then-Vice President Mike Pence.

According to the book, the president had a high comfort level with Kellogg, who "had the kind of look Trump liked for his generals," possessing a "straight jaw" and "a gruff manner of speaking." Trump reportedly felt at ease cursing around the retired lieutenant general, and one day, Kim was the target of his ire.

"I'm dealing with a fucking lunatic," Trump reportedly said during a meeting with Kellogg regarding his relationship with the North Korean leader.

The book did not say when the statement was made, but Kellogg became Pence's national security advisor in April 2018, the same month as the historic inter-Korean summit between Kim and South Korean President Moon Jae-in. Kellogg served in that capacity until January 2021.

The authors write that Kellogg was "torn between two worlds" as part of the Pence orbit, as well as Trump World.

"I make no bones about it. I'm a Trump loyalist," Kellogg reportedly told others, despite his post in Pence's office.

While the Trump administration early on sought to thaw their relationship with Kim, the pathway to doing so was not easy.

In September 2017, Trump called Kim "rocket man," which set off a stream of insults between the two men.

According to The Washington Post, the then-president remarked that he felt as though the comment could be taken as a compliment and not in a derogatory manner.

However, Trump previously called Kim a "maniac" who "actually has nuclear weapons" during a GOP presidential debate in September 2015.

In February 2016, he said that Kim was "a bad dude" who shouldn't be underestimated, and added: "I would get China to make that guy disappear in one form or another very quickly."

Kim was no slouch in the insult department, calling Trump "a mentally deranged US dotard" in September 2017 after the then-president threatened to "totally destroy" nuclear-armed North Korea as he gave his first address to the United Nations General Assembly in New York.

"He is surely a rogue and a gangster fond of playing with fire, rather than a politician," Kim said in response to Trump's comments.

While the relationship between the two men grew stronger over time, their push for a peace treaty did not produce a concrete deal that would lock in North Korea's denuclearization in exchange for sanctions relief.