Other alternatives? Last July, I asked then-C.I.A. Director Mike Pompeo to suggest some. “From the administration’s perspective,” he replied, “the most important thing we can do is … separate capacity, and someone who might well have intent, and break those two apart.”

It was an unmistakable call for regime change, and Pompeo promised that the intelligence community would provide “a wide range of options for the president about how we might go about that.” Apparently they came up short. Hence the interest in negotiation.

Yet the fact that all the options are bad does not, as some argue, make negotiations the “least bad” among them. Sanctions relief and economic concessions help keep the Kim regime in power and in business, funding the nuclear programs those concessions are supposed to stop.

Negotiations also dignify and legitimize a regime that, alongside Syria’s Bashar al-Assad, is the worst violator of human rights in the world today. Spare a thought, while watching the two Korean presidents behave like old friends, for the 80,000 to 130,000 prisoners enslaved in Pyongyang’s gulags.

Worst of all, the negotiations will tempt Trump to indulge his worst isolationist impulses. Last month, he again hinted that he would withdraw U.S. troops from South Korea if he doesn’t get better trading terms. That would have been music to Kim’s ear, since a fundamental goal of North Korean policy is to drive a wedge between Seoul and Washington.

A peace deal between the United States and North Korea to establish formal relations and end the Korean War would be hailed, even by many liberals, as a signal diplomatic triumph. Fox News would clamor for Trump to be awarded a Nobel Peace Prize. But it would advance a central aim of North Korean and Chinese foreign policy by undercutting the rationale for maintaining sizable U.S. forces in South Korea.