SEOUL, South Korea — Secretary of State Mike Pompeo told Asian powers on Thursday that President Trump was sticking to demands that North Korea surrender its nuclear weapons, and sought to hold together a fragile consensus on maintaining tough sanctions despite Mr. Trump’s declaration that the North was “no longer a nuclear threat.”
At a news conference in Seoul, South Korea, Mr. Pompeo softened some of the president’s recent comments — but did not retract them — and insisted that United Nations sanctions would remain in place until North Korea had accomplished “complete denuclearization.”
“We are going to get the complete denuclearization,” Mr. Pompeo told reporters. “Only then will there be relief from sanctions.”
Those remarks were intended to mollify the American allies Japan and South Korea and refute reports in North Korea’s state media that the United States would gradually ease sanctions against the North if it began to dismantle its nuclear weapons program.
They were also a clear message and appeal for cooperation to Beijing, where Mr. Pompeo was set to visit on Thursday night.
Mr. Pompeo’s remarks in Seoul came just two days after Mr. Trump met North Korea’s leader, Kim Jong-un, in Singapore for the first-ever summit meeting between the leaders of their two countries. In a joint statement signed there, Mr. Kim committed to the vague promise of “complete denuclearization” and Mr. Trump promised equally vague security assurances.
The document was glaringly light on details, including when and how North Korea would denuclearize and what it would do with its missiles.
Adding to global confusion were comments by Mr. Trump that the world can “sleep well tonight” because “there is no longer a nuclear threat from North Korea.” Mr. Pompeo said those remarks were made “eyes wide open.”
Mr. Trump also stunned American allies in the region when he announced Tuesday that he would end joint military exercises with South Korea, calling the war games the allies have conducted for decades “very expensive” and “provocative.”
In Seoul on Thursday, Mr. Pompeo met with his South Korean and Japanese counterparts to allay their fears that Mr. Trump gave away too much.
North Korean state media on Wednesday reported that Mr. Trump had agreed to lift sanctions when relations improved and agreed to “step-by-step” denuclearization, rather than immediate and total dismantlement.
Mr. Pompeo insisted the Singapore agreement, including plans for lifting sanctions, was no more vague than agreements made by previous administrations.
“The sanctions relief cannot take place until such time as we have demonstrated that North Korea has been completely denuclearized,” Mr. Pompeo reiterated.
“The sequence will be different this time,” he said, adding that Mr. Trump had made it clear to Mr. Kim that sanctions relief would only come after denuclearization.
Mr. Pompeo said the United States and its allies remained committed to achieving a “complete, verifiable and irreversible denuclearization of North Korea,” but said more negotiations to get there would be necessary. It will be “a process,” he said, adding, “not an easy one.”
The government of South Korea, which has been an eager supporter of Mr. Trump’s diplomacy with Mr. Kim, spared no praise on Thursday.
“This is the first time that the highest authority of North Korea promised to the president of the United States to work toward the complete denuclearization of the Korean Peninsula, which we believe has bolstered the political momentum for action to resolve the North Korean nuclear issue,” said Kang Kyung-wha, South Korea’s foreign minister.
On Thursday, President Moon Jae-in of South Korea indicated that his government supported Mr. Trump’s decision to end joint military exercises. Speaking at a meeting of his National Security Council, Mr. Moon said South Korea needed to be “flexible” about the exercises if North Korea started moving toward denuclearization.
In Tokyo, Prime Minister Shinzo Abe attached a similar significance to the summit meeting result.
“I think it is significant that regarding the nuclear issue first, Chairman Kim promised to President Trump the complete denuclearization of the Korean Peninsula,” Mr. Abe said. “I think that the U.S.-North Korea summit meeting was a step forward toward peace and stability in Northeast Asia.”
But Japan’s foreign minister, Taro Kono, struck a less enthusiastic chord, stressing that stability in the region could only be achieved when North Korea verifiably dismantled “all weapons of mass destruction and ballistic missiles of all ranges.”
Mr. Kono also suggested that a “pause” in joint military exercises between the United States and South Korea should be “contingent upon” North Korean action toward denuclearization.
Despite the confusion and wariness in the region, there was one clear winner from the political thaw on the Korean Peninsula: Mr. Moon of South Korea, who worked tirelessly to help make the Kim-Trump meeting happen.
On Thursday, the Democratic Party of Mr. Moon rode a wave of popular support for his peace initiative to win 14 of 17 elections for mayors and governors of big cities and provinces, including Seoul, routing the conservative opposition party Liberty Korea.
The elections took place one day after the Singapore summit meeting between Mr. Kim and Mr. Trump. Despite widespread skepticism, many South Koreans celebrated the meeting after months of living in the shadow of a possible war.
“Some analysts give a low score to the North Korea-United States summit, but that is far from how the people think of it,” Mr. Moon told Mr. Pompeo on Thursday.
In Beijing, where Mr. Pompeo was scheduled to meet Thursday evening with China’s president, Xi Jinping, an initial sense that the summit meeting had been a boon to China quickly disappeared.
“There are big uncertainties,” said Yang Xiyu, a former Foreign Ministry official who directed China’s relations with North Korea in the mid-2000s. “The big differences are on the step-by-step approach for denuclearization that North Korea wants. I am worried the U.S. will say they want everything done at once and then there is collapse.”
The absence of any mention of a longstanding American demand that North Korea must agree to verification of its nuclear dismantlement presented a major stumbling block to progress, he said.
“North Korea is nervous about verification and the U.S. wants verification,” he said.
Among Mr. Pompeo’s challenges will be to get the Chinese on board for maintaining sanctions.
China insists that United Nations sanctions should be eased, now that North Korea has come to the negotiating table.
“The U.N. Security Council resolutions that have been passed say that if North Korea respects and acts in accordance with the resolutions, then sanction measures can be adjusted, including to pause or remove the relevant sanctions,” said Geng Shuang, a Foreign Ministry spokesman.
Mr. Trump acknowledged on Tuesday that his trade dispute with China may have resulted in China’s lax enforcement of sanctions against North Korea.
“We’re having very tough talks on trade,” Mr. Trump said. “And I think that probably affects China somewhat. And I think, over the last two months, the border is more open than it was when we first started.”
Choe Sang-Hun reported from Seoul, South Korea, and Jane Perlez from Beijing. Motoko Rich contributed reporting from Tokyo.