On Friday morning, less than a day after Kim called Trump "deranged" and a "dotard," Trump took to Twitter to declare that the North Korean strongman is "obviously a madman."
"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 said.
Testy dialogue between the two countries is not unusual, but the rhetoric between Trump and Kim has grown particularly heated as tensions have escalated.
The U.S. hit North Korea with new sanctions this week to punish the country for its continued development of nuclear weapons, after Trump threatened to "totally destroy" North Korea during a speech at the United Nations. Pyongyang responded by threatening to detonate a hydrogen bomb in the Pacific.