President Trump is planning a second summit with North Korea’s Kim Jong-un. Fine. But what’s with all the president’s lovey-dovey words for the mad butcher of the North?

After all, sending Valentines to Mr. Kim won’t make him any more willing to disarm. Pyongyang is much more likely to react to increased pressure, as top Trump advisers are well aware, than to public displays of affection.

Fact is, the president’s unbecoming bromance with the North Korean strongman may be harming his own team’s efforts to maintain, and even ratchet up, pressure on Pyongyang until it verifiably and irreversibly gives up its nukes and intercontinental missiles.

“We went back and forth. Then we fell in love,” Mr. Trump gushed, in a stump speech last week. Speaking of Mr. Kim, he added, “He wrote me beautiful letters. And they are great letters. We fell in love.”

Isolated from the world as they are, North Korean bigwigs are no fools. When they hear love, they want it consummated.

“Without any trust in the U.S., there will be no confidence in our national security. And under such circumstances, there is no way we will unilaterally disarm ourselves first,” the North’s foreign minister, Ri Yong Ho warned the United Nations General Assembly on Saturday.

As Mr. Ri explained, Pyongyang has conducted no nuke tests or launched any missiles for a year; now it’s America’s turn to end its punishment of the North — or to forget about disarmament.

One can hardly blame Mr. Ri. Mr. Trump has told audiences over and over again that his threats and diplomacy stopped North Korea from testing nukes and missiles.

Yet the North’s year-long pause doesn’t resolve the issue. National Security Adviser John Bolton, Secretary of State Mike Pompeo, and our ambassador to Turtle Bay, Nikki Haley, have rightly made clear that this is no time to go soft.

“Enforcement of U.N. Security Council sanctions [on North Korea] must continue vigorously and without fail until we realize final, fully verified denuclearization,” Mr. Pompeo told the Council. He’ll meet Mr. Kim on Sunday to prepare for the upcoming summit, the State Department announced Tuesday.

Team Trump, led by Mrs. Haley, is trying to keep up the sanctions regime that the Security Council imposed in 2017. Those sanctions were so tough that, more than anything, they forced Kim & Co. to agree to negotiate seriously.

Last week, Russia’s foreign minister, Sergei Lavrov, urged the council to start phasing out those restrictions. As always, Moscow’s suave diplomat was ahead of the curve: The sanction regime that once united world powers is beginning to crumble, even without a formal decision to end it.

A report by an independent committee of experts charged by the Security Council with overseeing sanctions implementation has accused Russia and China of undermining one of the most important tools to press Pyongyang: limiting its ability to purchase energy.

According to the report, which was leaked to the press, Chinese and Russian companies helped North Korea exceed the Security Council’s annual cap of 500,000 barrels of imported oil. The experts also detailed several other gross sanctions violations.

(This being the UN, of course, Russia was able to edit its violations out of the report. Mrs. Haley, backed by Britain, France and others, is insisting on putting them back in. Thus, as of now, the report has yet to be made public.)

Meanwhile, the South Korean president, Moon Jae-in, the matchmaker in the Trump-Kim love affair, is pushing joint economic ventures with Pyongyang — and asking the Security Council to exempt his projects from the sanctions regime.

Mr. Moon’s appeasement clearly goes against the kind of pressure top Washington officials say is needed to achieve denuclearization. Yet his efforts are widely applauded worldwide. Bet on him to win the Nobel Peace Prize, and you won’t be sorry.

Mr. Trump, who should know better, will get no such prize. When he expresses his love for Kim, Russia, China, and South Korea only become more eager to reward the North.

In some cases — such as the negotiations over the new trade deal between the United States, Mexico, and Canada — Mr. Trump’s rhetorical excess is harmless, maybe even beneficial. Not so his self-defeating love affair with the devious, murderous tyrant scion of a devious, murderous tyrannical dynasty.

Mr. Trump’s cooing may well reverse the modest gains reached so far on the North Korea front. He shouldn’t be blinded: This love affair may end in disaster.

This column first appeared in the New York Post.