The leaders of Japan, the United States and South Korea on Sunday agreed to take "resolute steps" toward the complete denuclearization of North Korea as tensions have escalated recently over Pyongyang's flurry of missile tests.

After meeting with U.S. President Joe Biden and South Korean President Yoon Suk Yeol in Phnom Penh, Japanese Prime Minister Fumio Kishida also told reporters that the three-way cooperation is becoming more important than ever, given the possibility of further provocations by North Korea.

Amid fears that North Korea may soon go ahead with its seventh nuclear test and first since 2017, in defiance of international warnings, the leaders agreed to work together to strengthen deterrence with the three countries coordinating sanctions against Pyongyang, according to a joint statement.

While reaffirming that North Korea cannot avoid facing a "strong and resolute response from the international community" if another nuclear test is carried out, they also said in the statement that "the path to dialogue remains open toward peaceful and diplomatic resolution" with Pyongyang.

Combined photo shows (L-R) South Korean President Yoon Suk Yeol, U.S. President Joe Biden and Japanese Prime Minister Fumio Kishida during trilateral talks in Phnom Penh on Nov. 13, 2022. (Pool photo)(Kyodo)

White House National Security Adviser Jake Sullivan told reporters aboard Air Force One that the leaders "did coordinate on a joint response in the event that there would be a seventh nuclear test by (the North), and they tasked their teams to work out the elements of that response in real detail."

He said, "You can expect a trilateral response well-coordinated among the three countries" if that happens.

Ahead of the trilateral talks, Kishida and Biden held talks bilaterally for about 40 minutes and agreed to bolster their long-standing security alliance.

Kishida said he informed Biden of Japan's plan to "substantially increase" its defense budget, and the U.S president supported the idea.

The three-way and bilateral meetings took place on the fringes of summits involving the Association of Southeast Asian Nations and its partners.

Since Kishida, Biden and Yoon last met in late June, when they traveled to Madrid to be part of a North Atlantic Treaty Organization summit, North Koran has accelerated the pace of firing ballistic missiles.

In early October, a missile was fired over the Japanese archipelago for the first time in five years. Pyongyang also launched an intercontinental ballistic missile earlier this month.

Since Yoon succeeded left-leaning Moon Jae In in May, South Korea has adopted a harder stance toward North Korea and expressed a desire to strengthen defense cooperation with the United States and Japan.

The three countries conducted an anti-submarine exercise for the first time in five years in late September, as well as a joint drill to detect ballistic missiles in early October.

The statement said the leaders also discussed Russia's ongoing invasion of Ukraine and confirmed their commitment to a free and open Indo-Pacific, referring to the vision pushed strongly by Japan and the United States as a counter to China's rise.

Without naming China, the three leaders said in the statement they strongly oppose "any unilateral attempts to change the status quo in waters of the Indo-Pacific, including through unlawful maritime claims, militarization of reclaimed features, and coercive activities."

They also touched on Taiwan, which Beijing considers a breakaway province, and reiterated that maintaining peace and stability around the democratic island is an "indispensable element of security and prosperity in the international community."

Tensions over Taiwan remain high. Chinese President Xi Jinping said last month that the mainland will never renounce the right to use force to bring the island under its control.

On the back of China's expanding influence, the three nations said they will launch a dialogue on economic security.

As for the abduction of Japanese nationals by North Korea in the 1970s and 1980s, they reaffirmed a shared commitment to its immediate resolution.

The leaders will attend a summit of the Group of 20 major economies to be held on the Indonesian island of Bali for two days from Tuesday.

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