Trump’s comments triggered expressions of concern from China and from US allies, and stock markets and the dollar slipped as investors seek safe-haven investments.

Early Thursday North Korea reacted by saying Trump was not a reasonable man. It also elaborated on a threat to attack the tiny US Pacific territory of Guam.

“Sound dialogue is not possible with such a guy bereft of reason and only absolute force can work on him,” the official KCNA news service quoted General Kim Rak Gyom of the Korean People’s Army as saying.

The statement said the army would complete by mid-August a plan for the Guam attack, which would involve four rockets flying over Japan, and submit it to Kim Jong-Un for consideration as a “crucial warning to the US.”

US Defense Secretary Jim Mattis, who has often emphasized the devastating costs any conflict with North Korea could have, delivered a statement underscoring his boss’s language.

Mattis said North Korea must stop isolating itself and “stand down” in its pursuit of nuclear weapons, and Pyongyang “should cease any consideration of actions that would lead to the end of its regime and the destruction of its people.