Mr. Kim’s trip to the United States starts the most important negotiating track leading up to the summit meeting. Over the weekend, a team of American diplomats met with North Korean officials in the Demilitarized Zone, and White House logistics experts have been talking with North Koreans in Singapore about arrangements for the leaders’ meeting there.
But a trip to the United States by Kim Yong-chol — who has served the three leaders of the Kim dynasty that has ruled the North since 1945 — signaled that negotiations were reaching a critical point.
Mr. Kim would be the highest-ranking North Korean official to visit the United States since 2000, when Vice Marshal Jo Myong-rok invited President Bill Clinton to Pyongyang, with the prospect of sealing an agreement on curbing the North’s missiles. It never came to fruition.
A diplomat in Beijing, where Mr. Kim stopped overnight Tuesday, said it was not immediately clear whether the negotiator would meet with the Chinese again before going on to New York, where he is expected to arrive on Wednesday.
China’s Foreign Ministry would not confirm the former spymaster’s presence in Beijing, even though video footage showed him at the airport after his arrival from the North Korean capital, Pyongyang.
In recent weeks, China and the United States have been vying for the attention of Kim Jong-un, with Mr. Trump accusing China of contributing to a toughened North Korean stance on denuclearization after the North Korean and Chinese leaders met this month.
If the former spy chief met with senior Chinese officials in Beijing, he might risk angering Mr. Trump again, diplomats said. His stop in Beijing could also be related to his presence on a sanctions list that bars him from entering the United States.
An American diplomat said a waiver would have to be granted for such an individual to enter the United States, although it was likely one would automatically be given under extraordinary circumstances like these.
Mr. Kim was probably headed to New York, where North Korea has a mission to the United Nations, rather than to Washington because it was easier for him to get a visa there, another American diplomat said. North Korean diplomats and officials are not allowed to travel more than a few miles outside New York City.
Kim Yong-chol has already met Mr. Pompeo twice in Pyongyang. On the second visit, Mr. Pompeo expected to come away with a set of details for the Singapore summit meeting relating to the denuclearization of the North, but failed to do so. After the second meeting this month, Mr. Pompeo returned to Washington with three Americans who had been detained in North Korea.
In his most recent meeting with Mr. Pompeo, Mr. Kim struck a defiant tone, saying at a luncheon that North Korea’s willingness to enter into talks was “not a result of sanctions that have been imposed from the outside.” But he reminded the visiting Americans that North Korea intended to focus “all efforts into economic progress in our country.”
Mr. Kim has served as a senior manager of the North’s intelligence operations for nearly 30 years, according to the website North Korea Leadership Watch.
Mr. Kim’s rare combination of senior positions in the North’s highly stratified political and military apparatus makes him “one of the most powerful figures in North Korea,” it said.
He is also one of the longest serving senior officials of the Kim dynasty. Mr. Kim was involved in the 1990s in one of the earliest efforts to limit the North’s nuclear weapons. According to an account in “The Two Koreas,” by Don Oberdorfer and Robert Carlin, Mr. Kim was the toughest of negotiators on an accord that eventually failed in 1992.
At the time, Mr. Kim accused a South Korean diplomat of composing 90 percent of the language in the accord, it says, quoting him as saying, “This is your agreement, not our agreement.”
In the mid-2000s, he was assigned as head of the Reconnaissance General Bureau, the North’s spy agency, and paid particular attention to operations against South Korea. When he was chief of the North’s intelligence service in 2010, South Korea accused him of being responsible for blowing up a South Korean Navy vessel, killing 46 sailors. Five months later, the United States Treasury put Mr. Kim on the sanctions list.
In February, Mr. Kim was sent to the closing ceremony of the Winter Olympics in South Korea. He appeared in photographs seated behind Ivanka Trump, a stern expression on his face.
Over the past few months, the United States and North Korea have come closer than ever to holding the first summit meeting of the countries’ leaders. In March, Mr. Trump surprised many people when he accepted Kim Jong-un’s invitation to meet, which was relayed through South Korean envoys. But last Thursday in a letter to the North Korean leader, Mr. Trump abruptly canceled the meeting.
He then changed course again on Friday, saying that the meeting might take place as scheduled. Officials from the United States and North Korea have since started a whirlwind of working-level diplomacy to try to narrow a gap over how to denuclearize the North and salvage the planned meeting.
