U.S. Secretary of State John Kerry stepped up pressure Monday on North Korea to give up its atomic weapons program, saying key regional powers, including Pyongyang ally China, are all "absolutely united" in demanding nuclear disarmament.

Kerry made the comments on the eve of Asia's largest annual security conference, the 27-country Association of Southeast Asian Nation Regional Forum, which includes top diplomats from the U.S., North Korea and four other nations involved in long-dormant nuclear disarmament talks.

North Korea's nuclear ambitions are expected to dominate the security forum along with other issues such as South China Sea disputes.

Tension on the Korean Peninsula had spiked earlier this year after North Korea conducted its third nuclear test and issued a torrent of threats to attack the U.S. and South Korea in anger over toughened U.N. sanctions over the underground atomic blast. The country recently ratcheted down the rhetoric and offered to talk with its rivals but still has repeatedly vowed to expand its nuclear arsenal in the face of what it calls U.S. hostility.

China, North Korea's longstanding ally and main aid provider, has showed signs of frustration with its neighbor by supporting U.N. sanctions and cracking down on North Korean banking activity.

After meeting with his Chinese, South Korean and Japanese counterparts, Kerry told reporters Monday that "I want to emphasize ... all four of us are absolutely united and absolutely firm in our insistence that the future with respect to North Korea must include denuclearization."

"China made clear to me they have made very firm statements and very firm steps that they have taken with respect to the implementation of that policy," he said.

"We confirmed that there is a better path open to North Korea," Kerry said. "And we want North Korea to understand 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."

Earlier Monday, Chinese Foreign Minister Wang Yi said the six-nation disarmament talks need to be resumed to resolve the North Korean nuclear issue.

"We hope the relevant parties can work together toward the goal and bring the denuclearization back to the track of dialogues," Wang told reporters after private bilateral talks with his North Korean counterpart, Pak Ui Chun.

The nuclear disarmament talks — which involve the two Koreas, the U.S., China, Japan and Russia — have been stalled since North Korea pulled out of the negotiations in 2009 to protest international condemnation over a rocket launch.

As the ASEAN security forum includes all the six countries involved in the nuclear talks, it has previously provided a chance to use informal, sideline discussions to break stalemates over the nuclear standoff. In 2011, top nuclear envoys from the two Koreas met on the sidelines of the forum in Bali, Indonesia, and agreed to work toward a resumption of the six-nation talks.

It's still unclear whether such talks will take place in Brunei. South Korean and U.S. officials said they have no immediate plans to meet privately with Pyongyang.

North Korea has expressed its intention to rejoin the nuclear talks, but the U.S. and South Korea say North Korea first must demonstrate its sincerity on nuclear disarmament with concrete action.

Meeting ASEAN foreign ministers, Kerry also said Washington wants to see immediate progress on a proposed "code of conduct" between China and the 10-nation bloc to ensure regional stability amid long-raging territorial disputes in the South China Sea, among the world's busiest shipping lanes. The proposed pact aims to discourage aggressive acts that could set off armed confrontations.

Saying America does not take sides in the disputes, Kerry reiterated that the U.S. has a strong interest in the way the disputes were to be resolved "and in the conduct of the parties." Aside from China and Taiwan, four ASEAN members — Brunei, Malaysia, the Philippines and Vietnam — have long contested ownership of the resource-rich islands, islets, reefs and surrounding waters.

"As a Pacific nation, and the resident power, the United States has a national interest in the maintenance of peace and stability, respect for international law, unimpeded lawful commerce and freedom of navigation in the South China Sea," Kerry said. "What happens here matters to the United States."

Aiming to reassure allies, Kerry said the Obama administration would intensify its strategic "pivot" to Asia, including its political and security engagement with Southeast Asia.

"Let me be crystal clear: I know that some people have wondered whether in the second term of the Obama administration and with a new secretary of state, are we going to continue on the path that we have been on? And the answer, I say to all of you directly, is yes," he said. "Not just yes, but we hope to increase the effort."


Associated Press writers Deb Riechmann in Bandar Seri Begawan, Brunei, and Jim Gomez in Manila, Philippines, contributed to this report.