[How Vietnam offers a model for North Korea’s relations with the United States.]

Mr. Trump visited Danang, Vietnam, for the first time in 2017 when he attended an annual summit meeting of the Asia-Pacific Economic Cooperation forum. As the site for his upcoming meeting with Mr. Kim, Vietnam offers a couple of possible allegorical lessons: On the one hand, it was the setting of the United States’ last major war in the region, a reminder of the devastating costs of conflict. On the other, it represents how a Communist regime can emerge from international isolation and build a thriving economy.

The forthcoming meeting is fraught for Mr. Trump, who has made a possible agreement with North Korea one of the signature goals of his foreign policy. After Singapore, he claimed prematurely that the North Korean nuclear dispute was “largely solved.” He regularly boasts of his close relationship with Mr. Kim — “we fell in love,” he once said — and regales visitors about the friendly letters he has received from the North Korean dictator.

As evidence of their rapprochement, Mr. Trump regularly notes that North Korea released three American prisoners and sent back what were believed to be the remains of 55 American soldiers who died in the Korean War.

But many experts have said North Korea is simply stringing Mr. Trump along, taking advantage of his inexperience and his desire for a breakthrough. His own intelligence chiefs told Congress last week that North Korea is “unlikely to completely give up its nuclear weapons and production capability,” as Mr. Trump has been seeking.

“That’s what the intelligence chief thinks, and I think there’s a good possibility of that, too,” Mr. Trump said in an interview broadcast over the weekend on “Face the Nation” on CBS. “But there’s also a very good chance that we will make a deal. I think he’s also tired of going through what he’s going through. He has a chance to have North Korea be a tremendous economic behemoth. It has a chance to be one of the great economic countries in the world.”