President Donald Trump on Saturday night fired back at a forceful speech given by North Korea’s foreign minister earlier that day.

“Just heard Foreign Minister of North Korea speak at U.N. If he echoes thoughts of Little Rocket Man, they won’t be around much longer!” Trump said on Twitter.

Trump in recent days has been using the nickname “Rocket Man” to refer to North Korean leader Kim Jong Un, including in his own speech at the United Nations.

North Korea’s foreign minister, Ri Yong Ho, had accused Trump of being “a mentally deranged person full of megalomania” who is holding “the nuclear button.” He added that Trump’s recent insults made “our rocket’s visit to the entire US mainland inevitable all the more.”

Tensions have escalated in recent months between the US and North Korea, as the reclusive nation continues to ramp up its nuclear weapons program. North Korea recently tested what it said was a hydrogen bomb and fired a missile over Japan.

Trump heightened his own rhetoric during his first-ever speech to the United Nations' General Assembly this week, threatening that if North Korea does not deescalate its nuclear aggression, the US will "have no choice but to totally destroy North Korea."

"Rocket man is on a suicide mission for himself and for his regime," Trump said.