U.S. Secretary of State John Kerry says the United States, China, Japan and South Korea are "absolutely united" in their insistence that North Korea denuclearize.
Kerry said Monday after meeting with Chinese Foreign Minister Wang Yi in Brunei that the only way to ensure peace and stability in the region is for North Korea to live up to its agreement from prior six-party talks to denuclearize.
"That the region will be better with the denuclearization and the possibilities of normal relationships, not just between the south and the north or china and North Korea, but between the United States and North Korea and the rest of the world, lies at the end of engaging in a serious set of steps to denuclearize and serious negotiations that could accompany that."
Kerry also met Monday with the foreign ministers of Japan and South Korea as part of two days of meetings with the 10-member Association of Southeast Asian Nations and other envoys.
Earlier, he urged ASEAN to make progress on a code of conduct covering disputes over the South China Sea.
Kerry said the United States has a strong interest in maintaining peace, security and free navigation in the South China Sea, where several nations have rival territorial claims.
"As we have said many times before, while we do not take a position on a competing territorial claim over land features, we have a strong interest in the manner in which the disputes of the South China Sea are addressed and in the conduct of the parties. We very much hope to see progress soon on a substantive code of conduct in order to help ensure stability in this vital region.''
On Sunday, Philippine Foreign Secretary Albert del Rosario renewed criticism of China for what he called a "massive" military buildup aimed at seizing control of energy and fishing rights in large parts of the South China Sea.
Kerry will meet Tuesday with Turkish Foreign Minister Ahmet Davutoglu and Russian Foreign Minister Sergei Lavrov to discuss the situation in Syria. His meeting with Lavrov will also include Moscow's decision not to return Edward Snowden, who leaked security secrets, back to the U.S. to face espionage charges.
North Korea has in recent weeks proposed restarting the stalled talks, which until 2008 provided the cash-strapped country with crucial energy and food aid in exchange for shuttering its nuclear program.
Pyongyang quit the talks that year and triggered international condemnation with a nuclear test in 2009 and a second test earlier this year.