Maybe such an unorthodox summit meeting between two leaders with a flair for the dramatic will be hugely successful; it could also collapse in failure, making it a very high-stakes gamble for Mr. Trump.

The North Koreans have been seeking a meeting with an American president for decades, yet Mr. Trump agreed to one without getting anything in return.

And it didn’t take long for the chaos and mixed messaging that has long characterized Trump policy to resurface Friday when Sarah Huckabee Sanders, the White House press secretary, seemed to back away from the summit meeting, insisting it wouldn’t take place unless North Korea first took concrete steps toward denuclearization. Of course, that didn’t last. Later, a White House official told The Wall Street Journal, “The invitation has been extended and accepted, and that stands.”

The planned session builds on an agreement, announced this week, for the United States and North Korea to hold their first sustained direct talks in many years. After a period of aggressively testing nuclear devices and missiles, Mr. Kim opened the door to talks by promising to discuss ending his nuclear program if America guarantees the North’s security. He agreed to suspend nuclear and missile tests during the talks and not to object when the United States and South Korea hold military exercises this spring.

Many assumed the next step would be preparatory talks in which experts from each side would test the other’s intentions and then enter into lengthy formal negotiations. What happens now is anybody’s guess.

A White House official provided Trumpian bluster on Thursday, saying that “we’re not even talking about negotiations” but rather a meeting between Mr. Trump, who “made his reputation on making deals,” and an authoritarian North Korean leader who has the power to make decisions and therefore avoid the “long slog of the past” negotiations. But the long slog of negotiations has a purpose, allowing the two sides to stake out positions, sometimes in public, then horse-trade privately as they search for a mutually acceptable bottom line. There is reason summit meetings are usually saved for the end, when leaders can give the last push to make a deal happen.

Let’s hope that responsible American officials are not approaching the talks with a serious belief in the skills of a businessman whose impetuousness helped lead to several bankruptcies and who revealed sensitive intelligence secrets to Russian officials during an Oval Office meeting.