Jae H. Ku, director of the U.S.-Korea Institute at the Johns Hopkins School of Advanced International Studies, agreed that moves toward diplomacy would be delayed. “I think it’s going to be slowed down. There is going to be a lot of anger and venting of frustrations,” he said.
But other analysts said that however horrific the case might be, the Trump administration was unlikely to let it upset the momentum toward dialogue it has built in recent months. They said that Mr. Yun’s trip was the first fruit of those efforts and that North Korea may have freed Mr. Warmbier to open up space for diplomacy with Washington, even if they anticipated the anger that his condition would provoke in the United States.
A statement on Monday from Mr. Trump about Mr. Warmbier condemned the North for its “brutality,” but he and Secretary of State Rex W. Tillerson both stopped short of announcing fresh sanctions in response.
Mr. Warmbier was visiting North Korea as part of a tour group when he was detained at the Pyongyang airport in January 2016. Two months later, he was sentenced to 15 years of hard labor for the “hostile act” of trying to steal a propaganda poster off the wall of his hotel.
In a series of low-key communications with the North Koreans in recent months, the Trump administration pushed for the release of Mr. Warmbier and the three other Americans as a first step toward improving ties, according to South Korean officials and others familiar with the process, who spoke on the condition of anonymity because of the sensitivity of the matter.
When Mr. Yun held a secret meeting with Choe Son-hui, a senior negotiator from the North Korean Foreign Ministry, in Oslo last month, the North Koreans agreed to look into the matter, these people said. But this month, the North Koreans came back with shocking news: They said Mr. Warmbier had been in a coma for more than a year and told the Americans to take him home.
North Korea has said it released Mr. Warmbier on “humanitarian grounds” but did not explain his medical condition. It has told American officials that Mr. Warmbier fell into a coma after contracting botulism, according to his family.
American doctors found “extensive” brain damage but could not say what had caused the injury. They found no evidence of botulism, or that Mr. Warmbier had been beaten, as one American official had asserted.
“Perhaps his condition deteriorated and the authorities decided it was better to release him in a coma than as a corpse,” said John Delury, a North Korea expert at Yonsei University in Seoul. “North Koreans might have feelers out to see if there is a deal to be made with the Trump administration, and releasing Mr. Warmbier is a way to move that process along, while also removing what could be an obstacle down the road.”
Mr. Warmbier’s death comes at a delicate time in international diplomacy surrounding North Korea. Senior Chinese and American officials are due to meet in Washington this week, and United States officials planned to press their counterparts to do more to rein in Pyongyang’s nuclear pursuits.
China, North Korea’s main ally, is a strong advocate for negotiations over the North’s nuclear program, and Mr. Warmbier’s death seemed unlikely to change that. At a daily news briefing in Beijing, a Foreign Ministry spokesman, Geng Shuang, called the death “really a tragedy” but stopped short of reprimanding North Korea for its treatment of Mr. Warmbier.
Shi Yinhong, a professor of international relations at Renmin University in Beijing, said that China would not punish North Korea over a human rights issue. “What makes China take steps is a missile or nuclear test, not the death of an American student,” he said.
Another Chinese analyst, Cheng Xiaohe, an associate professor of international relations at Renmin University, said Mr. Warmbier’s death illustrated the “failure of North Korea’s hostage diplomacy” because it would strengthen “hard-liners” in the Trump administration. He said there could be retaliation from the United States unless Pyongyang took a step like freeing the three remaining American captives.
“I believe the U.S. will not let the issue slip away quietly and will take retaliatory actions soon if North Korea fails to make a conciliatory move regarding the detainees,” he said.
Mr. Warmbier’s case has drawn new attention to the other three American prisoners in North Korea, who Mr. Yun was allowed to meet when he visited Pyongyang.
They are Tony Kim, a volunteer accounting teacher in his mid-50s who had taught at the Pyongyang University of Science and Technology, arrested in April for unknown reasons; Kim Hak-song, who also worked for the same university and did agricultural work, also arrested for unknown reasons, in early May; and Kim Dong-chul, 63, a businessman who has been serving a 10-year sentence of hard labor since April 2016, on spying charges.
Six South Koreans and a Korean-Canadian also remain in North Korean captivity on various criminal charges. South Korea’s president, Moon Jae-in, said on Tuesday that his government would redouble efforts to free the South Koreans from the North. He also sent a message of condolences to the Warmbier family, saying it was “deeply deplorable that North Korea does not respect the universal standards and values of human rights,” according to his office.
Mr. Moon, who took office in May, is more open to dialogue with North Korea than any of his recent predecessors. He is scheduled to meet with Mr. Trump in Washington this month and is expected to urge the president to talk to Pyongyang, saying that sanctions alone have failed to change the North’s behavior. But South Korean officials feared that idea would be a harder sell after Mr. Warmbier’s death.
Still, there was cautious hope here that if North Korea and the United States negotiated the release of the other three Americans, it could eventually pave the way for far more complicated talks over how to contain or dismantle North Korea’s nuclear weapons programs.
“Over the years, South Koreans have grown weary as tensions kept rising and the North’s nuclear program kept advancing,” said Yang Moo-jin, a professor at the University of North Korean Studies in Seoul. “There is a growing sense that we needed change, a breakthrough.”