“In some ways there’s a symmetry,” said Wendy R. Sherman, a longtime former diplomat who was part of a historic American delegation to Pyongyang under President Bill Clinton and later negotiated the Iran nuclear agreement for President Barack Obama. “You have two leaders who believe fundamentally that they are the only people who matter.”

Other presidents left talks with North Korea to lower-level officials because they did not want to reward Pyongyang with the prestige of such a meeting unless there was a substantial assurance of a breakthrough. They feared an ill-conceived gathering that resulted in failure would be counterproductive…

“I can’t imagine any other president doing this on the basis of these general comments passed on from Kim Jong-un,” said Christopher R. Hill, who negotiated with North Korea for President George W. Bush. “The question is whether Trump will go ahead without clear signs the North Koreans are on the way to denuclearization.”