But no sooner had the North and the United States declared their willingness to talk to each other — something they have in fact done before — than it became clear that the two sides remained stubbornly far apart.

“The North Koreans have always said they would be happy to talk to the United States, and in fact they are eager to come and talk to us — as one nuclear weapons state to another,” said Ralph Cossa, president of the Pacific Forum at the Center for Strategic and International Studies. “And the U.S. is willing to talk to the North Koreans if they are prepared to put nuclear weapons on the table. So both sides are willing to talk, but not about the same thing.”

While leading the United States delegation to the Olympics in Pyeongchang, South Korea, earlier this month, Vice President Mike Pence planned to secretly meet with a high-level delegation from North Korea, but the North Koreans canceled at the last minute, according to the State Department.

“This is the real challenge with North Korea,” said Mr. Cossa. “If you try to confront them, they get their backs up and feel they have to be more confrontational back, to show they are not afraid.”

”But if you make an overture, they see this as a weakness they have to exploit,” he added. “And if you offer them the moon and the stars, they say ‘O.K., we want the sun also.’”

The United Nations Security Council has imposed increasingly strict sanctions on North Korea over its weapons program, but policing violations can be difficult. On Tuesday, Japan’s Foreign Ministry announced that a Japanese military plane on Saturday had detected a North Korean and a Maldavian-flagged ship conducting what Japan judged to be ship-to-ship transfers banned by the Security Council.

Image Joseph Y. Yun, one of the U.S. State Department’s most knowledgeable and experienced diplomats on North Korea, abruptly announced that he would retire by the end of the week. Credit... Yonhap/European Pressphoto Agency

Many analysts say that the North Korean leadership will never agree to talks if they have to promise to give up their nuclear weapons to get the dialogue started.