The foreign ministers of North and South Korea met Saturday for the first time since nuclear disarmament talks collapsed in acrimony three years ago, but the U.S. warned at Asia's largest security gathering that much difficult diplomatic work lies ahead.

Delegates also discussed flare-ups and territorial disputes in the South China Sea and the slow pace of reforms in Myanmar.

A day after discussions between nuclear negotiators for the two Koreas _ the first after more than a year of confrontation and escalating threats _ South Korean foreign minister Kim Sung-hwan and the North's Pak Ui Chun walked together and chatted as they headed into the ASEAN Regional Forum.

That further lifted hopes for a return to multination nuclear disarmament negotiations.

Ahead of the conference, China and its Southeast Asian neighbors also agreed to a preliminary plan to resolve territorial disputes in the potentially resource-rich South China Sea _ but tensions remain high.

There have been several flare-ups in recent months, with Beijing usually accused of being the instigator.

China claims the waterway _ of tremendous strategic importance to everyone because one-third of the world's shipping transits through it _ in its entirety. But several Southeast Asian nations dispute that.

Leading the American delegation at the meeting on the Indonesian resort island of Bali, U.S. Secretary of State Hillary Rodham Clinton urged all parties to show restraint in the waterway and to comply with international law "and resolve their disputes through peaceful means."

It's vital, she said, that they work together and "resolve their disputes through peaceful means."

As a starting point, the U.S. wants all nations to map out their claims in terms consistent with customary international law, said Kurt Campbell, the top U.S. diplomat for Asia.

Also on the table was Myanmar and reforms it needs to take to win back international confidence.

That country, also known as Burma, held elections late last year, officially handing power to a civilian administration after a half-century of military rule. Pro-democracy leader Aung San Suu Kyi was released from house arrest. But many see the changes as cosmetic and believe the army will continue to hold sway.

Clinton told diplomats from 26 other Asian and European countries that she was encouraged to see that dialogue was starting to open between North and South Korea.

"But we remain firm that in order for six-party talks to resume, North Korea must take steps to improve North-South relations," she said, referring to the talks on the North's nuclear program that include the two Koreas, the U.S., China, Japan and Russia.

"North Korea continues to present a critical proliferation challenge to the international community and to threaten regional stability with its provocative actions," she said.

She said the U.S. urged the North to "demonstrate a change in behavior, including ceasing provocative actions" and "taking steps toward irreversible denuclearization."

North Korea's newly appointed envoy, Ri Yong Ho, said Friday that he and his South Korean counterpart, Wi Sung-lac, agreed during their meeting to work together to quickly restart nuclear talks.

Wi, who described the talks as "productive" and "helpful," confirmed the agreement and said he and Ri would continue their efforts.

North Korea stands to get badly needed aid and other concessions if it returns to the talks and has indicated in recent months that it may be ready.

North Korea's main ally, China, has been pressing for a speedy resumption of the talks. The U.S. and other countries have held out, saying that meaningful North-South dialogue must occur first. A senior U.S. official welcomed Friday's meeting but said it remains to be seen if the rapprochement is enough to warrant a return to the table.

The official, speaking on condition of anonymity to discuss closed-door diplomacy, said Clinton and the foreign ministers of Japan and South Korea would meet in Bali on Saturday to assess the situation and plot a way forward. The official would not predict if a decision on resuming the six-party talks would be made at the meeting.

In a meeting with Chinese Foreign Minister Yang Jiechi, Clinton affirmed "our mutual desire for peace and stability on the Korean peninsula" but offered no hint on whether the U.S. would agree to resume the nuclear talks.

Yang, however, signaled China's intense interest in getting things back on track. "Anything we can do together to promote better atmosphere and good dialogue among the parties concerned and to work together to restart the six-party talks would be in the best interests of peace, stability and security of the region," he said.

The disarmament talks have been stalled since 2008, when North Korea walked out to protest international criticism of a prohibited long-range rocket launch. Tensions between the North and South have remained high ever since.

Progress was reported on another major security front, with the draft deal between China and ASEAN over the South China Sea.

"I want to commend China and ASEAN for working so closely together to include implementation guidelines for the declaration of conduct in the South China Sea," Clinton told Yang.

Yang said he believed the agreement would go "a long way" in promoting "peace and stability" in the South China Sea. "This will of course provide favorable conditions for the proper handling and settlement of disputes among claimants," he said.

China has been accused in recent months of trying to block oil exploration by the Philippines and Vietnam in waters that are partially claimed also by those two countries and Taiwan, Brunei and Malaysia. Beijing long has resisted calls for a binding code of conduct that would require disputes in the waterway to be solved peacefully and without threats of violence.

Last year, Clinton angered China by saying resolution to the disputes was in the U.S. national security interest because of Washington's desire to guarantee navigational safety and maritime security in the South China Sea. She made the matter a central point of her participation in the East Asia Summit hosted by Vietnam, something that President Barack Obama is expected to restate when he attends that event this year.

Clinton's meeting with Yang appeared friendly, unusual given that Beijing just last week angrily condemned the White House meeting between Obama and the Dalai Lama, the exiled spiritual leader of Tibet, which China claims as a province.