Envoys from North and South Korea who met on the sidelines of a summit of Asian foreign ministers Friday said they had agreed to push for a revival of stalled six-party talks on nuclear disarmament by the North.

“We have agreed to make efforts to resume six-party talks as soon as possible,” North Korean diplomat Ri Yong Ho told reporters. Ri’s appointment as the North’s new envoy to the talks was made public earlier in the day.

His South Korean counterpart, Wi Sung-lac, called their meeting “constructive and useful.”

U.S. officials hailed the meeting as important but tempered their assessments with caution.

“There’s no determination to rush into anything. When you’re dealing with the North Koreans, understanding the importance of patience is clearly a virtue,” said a senior State Department official with knowledge of the talks who was not authorized to give his name. “The fact that they met in a high-profile setting . . . as opposed to some secret setting probably has some significance.”

The talks — comprising the two Koreas, the United States, China, Japan and Russia — stalled in 2008, with the North Koreans eventually walking out to protest international criticism of a banned rocket launch.

Since then, tensions have escalated as North Korea detonated a nuclear weapon in a test, allegedly torpedoed a South Korean ship and bombarded military personnel and civilians on a South Korean island.

In November, North Korea also revealed to a U.S. scientist its uranium enrichment program, which gives the country another path to manufacture nuclear weapons.

But in recent months, the North has signaled a desire to return to the talks, which could lead to the isolated and authoritarian country giving up parts of its nuclear program in exchange for much-needed aid. The face-to-face meeting Friday occurred at a summit of Asia’s largest security forum, the Association of Southeast Asian Nations, or ASEAN.

As recently as Thursday, however, Sung Kim, the U.S. special envoy to the six-party talks and the nominee to be the next U.S. ambassador to Seoul, said the United States was “not convinced that [the North Koreans] really are ready to return to serious diplomacy and negotiations.”

“This is why I think Seoul and Washington have both been very cautious in just rushing back to the negotiating table,” Kim said.

Given those doubts, the next step for the United States will be to discuss the situation with South Korea and Japan, the senior State Department official said, adding that the three countries will hold a meeting Saturday that probably will be dominated by the North Korea issue.

Just before the two Korean sides met, the United States and China — one of North Korea’s few allies — discussed the issue at a sideline meeting of their own.

Secretary of State Hillary Rodham Clinton said she and Chinese Foreign Minister Yang Jiechi had focused on their “mutual desire for peace and stability on the Korean Peninsula.”

Yang agreed, saying, “Anything we can do together to promote a better atmosphere and good dialogue among the parties concerned and to restart the six-party talks would be in the best interests of peace, stability and security.”

At the meeting, Yang also expressed Chinese displeasure over two perennial sore points: that President Obama and other U.S. leaders had met with the Dalai Lama in Washington this month and that the United States was considering selling fighter jets to Taiwan.

Meanwhile, Clinton brought up China’s controversial claims in the South China Sea, which is believed to hold valuable oil and minerals.

In recent weeks, Chinese forces have been accused of firing on Filipino fishermen, following a Filipino oil exploration ship and cutting the exploration cables of a Vietnamese ship. Six countries claim portions of the territory, with China’s claim by far the largest, encompassing almost the entire region.

On Thursday, China and other countries at ASEAN agreed on a vague, nonbinding guideline of conduct for the South China Sea.

“We welcome this. . . . It has lowered tensions,” U.S. Assistant Secretary of State Kurt Campbell said. “It has improved atmospherics. But clearly it is just that, a first step.”

The Philippines has pushed for the United States to weigh in more aggressively on the issue, asking for clarification on whether a mutual defense treaty between it and Washington means the United States is required to defend Filipino claims in the contested territory.

“We have clear treaty obligations,” said a U.S. official at the summit, also speaking on condition of anonymity. “But it is also the case that we do not want to stoke tensions.”

Harlan reported from Tokyo.