China, which has been enforcing United Nations economic sanctions against North Korea, its longtime but wayward ally, urged the two Koreas and other countries to “maintain the momentum for dialogue and work together to promote the denuclearization of the peninsula.”
“China welcomes it and extends its congratulations,” Lu Kang, the spokesman for the Ministry of Foreign Affairs, said of the accord.
The Japanese prime minister, Shinzo Abe, described the commitment to denuclearization as a “positive move toward the comprehensive settlement of various issues surrounding North Korea.”
In Russia, the Kremlin hailed the agreement as “very positive.” Dmitri S. Peskov, spokesman for President Vladimir V. Putin, said Mr. Putin “has stressed many times that sustainable conflict resolution on the Korean Peninsula can only be based on direct dialogue of both sides.”
The accord set no timetable for denuclearization but said that the two sides planned to achieve a permanent peace within the year. Talks to end the 1950-53 Korean War would require negotiations involving the main combatants: North and South Korea, China and the United States.
In Japan, there was caution about the lack of specifics in the inter-Korean accord. The document fell far short of the Trump administration’s demands for the dismantlement of the North’s arsenal and of the need for inspections to verify that the weapons no longer existed, officials and commentators said.
The Japanese foreign minister, Taro Kono, called for North Korea to take “concrete actions for the dismantlement of all weapons of mass destruction, including biological and chemical weapons, and ballistic missiles of all ranges in a complete and irreversible manner.”
Analysts in the Japanese news media also expressed doubts that Friday’s meeting was more than symbolic.
“Harmony was fully shown, but it’s a big mistake to interpret that there was big progress substantially,” an editorial in the right-leaning newspaper Sankei said, adding, “It’s very doubtful that the ‘denuclearization’ mentioned in the joint statement matches what has been discussed between Mr. Abe and Mr. Trump.”
Mr. Abe, who has strained relations with South Korea, implied that the new accord may not be too different from a similar commitment in 2007 between a previous South Korean president, Roh Moo-hyun, and Kim Jong-il, the father of the current North Korean leader. That accord fell apart soon after it was signed.
“We would like to think about how we respond to the current statement, analyzing and comparing it with the past statement,” Mr. Abe said.
Of all the North’s neighbors, Japan is perhaps the most uneasy about the process that began at the inter-Korean summit meeting. It fears Washington could agree to trade away the North’s long-range intercontinental missiles that can hit the United States, but allow Pyongyang to keep its medium-range missiles, leaving Japan vulnerable.
Mr. Abe went out of his way to remind reporters that he had spent 11 hours with Mr. Trump this month, insisting his proximity to the American president meant he had not been left out of the negotiations over North Korea.
On Saturday morning, President Trump wrote in a Twitter post that he “just had a long and very good talk with President Moon of South Korea,” and added that he had also spoken with Mr. Abe “to inform him of the ongoing negotiations.”
In China, the state-run news media, which generally reflects the attitudes of the government, stressed the need for the United States to quickly enter the picture and seal the deal made between South Korea’s president, Moon Jae-in, and Mr. Kim.
“The Kim-Moon summit will write the goal of denuclearization and strive to end the state of war in the Declaration of Panmunjom,” one Chinese newspaper, the Global Times, said in an editorial. “But they are all writing about the vision rather than the exact plan.”
Cheng Xiaohe, a professor of international relations at Renmin University, said it was too much to expect the two Korean leaders to come up with a definitive prescription for ending the North’s nuclear program in just one day.
“Kim Jong-un has to leave some gifts for Trump,” Mr. Cheng said. “This summit got a lot of results for an inter-Korean meeting.”
But there was no question that China remained sidelined in the rapprochement between North and South, and it was nowhere to be seen in the prelude to the meeting between Mr. Trump and Mr. Kim, said Shen Zhihua, a prominent Chinese historian who has written extensively on North Korea.
North Korea’s goal was to keep its nuclear weapons and to be recognized as a nuclear power, Mr. Shen said in an interview broadcast by Voice of America.
In the end, the North could persuade other countries to let it keep its nuclear arsenal, or at least part of it. And in the process, Mr. Shen said, China could be left permanently on the outside — with North Korea leaning toward the United States.
“Many Chinese people are very optimistic now,” he said, but added: “It does not seem that simple. If North Korea holds a nuclear weapon, it will not hit South Korea. Will it hit Japan? It does not dare. It also will not dare to fight the United States. If you look at history, North Korea is not sure about China and has a mind of revenge toward China.”
In addition, families of Japanese citizens abducted by North Korean spies four decades ago had hoped that Mr. Moon would raise the issue in his meeting with Mr. Kim. That seemed a distant hope. Human rights activists who asked Mr. Moon to get commitments from Mr. Kim on reforming the North’s vicious prison system were also disappointed.
Speaking to reporters in front of his home in Saitama, a suburb of Tokyo, Shigeo Iizuka, a brother of Yaeko Taguchi, one of the kidnapped, said that he was “disappointed” the abductions were not mentioned in the joint statement.
The summit meeting, Mr. Iizuka said, “was a big event that will be remembered as a page of history. I got the impression it was a superficial performance without substance.”