President Trump and North Korean leader Kim Jong Un have unleashed personal attacks on one another after the U.S. commander in chief’s speech at the United Nations.

“Kim Jong Un of North Korea, who is obviously a madman who doesn’t mind starving or killing his people, will be tested like never before!” Trump wrote Friday morning.

Hours earlier, Kim delivered a barrage of epithets against Trump, calling “mentally deranged” and “a gangster fond of playing with fire,” according to the New York Times.

Kim also branded Trump a “dotard,” defined by Merriam-Webster as a “person in his or her dotage,” with dotage meaning “a state or period of senile decay marked by decline of mental poise and alertness.”

Donald Trump; Kim Jong Un (Photos: Brendan Smialowski/AFP; Getty Images, KCNA via Reuters)

The North Korean leader’s statement came after Trump’s fiery speech at the United Nations General Assembly earlier this week, when he warned that the U.S. may “have no choice but to totally destroy North Korea.”

“Rocket Man is on a suicide mission for himself and for his regime,” Trump said, employing a newly coined moniker for Kim to denounce the country’s nuclear and intercontinental ballistic missile programs.

In the past, Trump has praised Kim as a “pretty smart cookie” and said he’d be “honored” to meet with the North Korean leader “under the right circumstances.”

Kim has since launched a series of provocative tests, including one of what Pyongyang claims was a hydrogen bomb capable of hitting the U.S. But experts question whether North Korea’s missiles have accurate guidance systems or the technology to reenter the atmosphere without burning up.