President Yoon Suk Yeol (left) speaks during a trilateral summit with U.S. President Joe Biden and Japanese Prime Minister Shigeru Ishiba at the Lima Convention Center in Lima, Peru, on Friday. (Yonhap)

The leaders of South Korea, the United States and Japan announced the establishment of a secretariat for trilateral cooperation and condemned North Korea and Russia's decision to "dangerously expand" Moscow's war in Ukraine as they met on the margins of a multilateral summit in Peru.

President Yoon Suk Yeol, US President Joe Biden and Japanese Prime Minister Shigeru Ishiba issued a joint statement after they held a trilateral meeting in Lima on the margins of the Asia-Pacific Economic Cooperation (APEC) summit.

During the last such gathering before Biden leaves office in January, the leaders reaffirmed their commitment to the trilateral partnership, which they believe remains critical to countering regional security threats and fostering stability in the Indo-Pacific.

"Today, we announce the establishment of the Trilateral Secretariat responsible for coordinating and implementing our shared commitments," the three leaders said in a joint statement.

"This new secretariat will seek to ensure that the work we do together further aligns our objectives and actions to make the Indo-Pacific a thriving, connected, resilient, stable, and secure region," they added.

Touching on the envisioned launch of the secretariat, the leaders stressed the three countries' partnership as one that is "built to last."

The three leaders also used the meeting to decry the North's troop dispatch to support Russia's war against Ukraine. Seoul and Washington have confirmed that North Korean troops, deployed to Russia's western front-line Kursk region, have begun engaging in combat operations against Ukrainian forces.

"Japan, the ROK, and the United States strongly condemn the decisions by the leaders of the DPRK and Russia to dangerously expand Russia's war of aggression against Ukraine," they said, referring to the official names of South Korea and North Korea, the Republic of Korea and the Democratic People's Republic of Korea, respectively.

"Deepening military cooperation between the DPRK and Russia, including munitions and ballistic missile transfers, is particularly egregious given Russia's status as a Permanent Member of the UN Security Council."

The leaders also reaffirmed their commitment to the "complete denuclearization of the Korean Peninsula."

According to a pool report from the White House press corps, a senior US administration official said that during the summit, the leaders paid their keenest attention to the growing threats from North Korea

"The issue that they probably discussed most in depth was the growing threat posed by the DPRK, both the DPRK growing missile and nuclear capabilities, and also, of course, the really escalatory and destabilizing nature of Russia-DPRK cooperation, particularly the deployment of North Korean troops into the Kursk region," the official told reporters.

The leaders said their countries need to continue to "very closely" follow the "concerning" developments about military cooperation between the North and Russia, and coordinate "more closely than ever before" on how to respond to it, according to the official.

In his opening remarks, Yoon underlined the importance of continued three-way cooperation.

"In the face of global complex crises, Korea-US-Japan cooperation not only aligns with the national interests of all three countries but is also essential for peace and prosperity in the Indo-Pacific region," Yoon said.

"The grave security environment, as evidenced by North Korea's recent deployment of troops to Russia, underscores once again the importance of trilateral cooperation," he added.

During the meeting, Yoon highlighted the active high-level consultations among Seoul, Washington, and Tokyo, emphasizing the establishment of a trilateral secretariat as a pivotal step in strengthening cooperation and implementing shared commitments.

"Trilateral cooperation has now evolved beyond security into a comprehensive and institutionalized partnership, encompassing areas such as the economy, advanced technologies like artificial intelligence, and quantum computing, as well as exchanges for future generations," Yoon said, hoping that the secretariat will serve as a "solid foundation" for deeper cooperation among the countries.

The secretariat will coordinate and oversee cooperation projects across various fields, including security, economy, advanced technologies, and people-to-people exchanges, Principal Deputy National Security Adviser Kim Tae-hyo said in a briefing.

The three countries will rotate the presidency every two years, with South Korea's foreign ministry set to establish the secretariat soon.

The meeting follows the historic Camp David Summit in August 2023, where Biden, Yoon, and former Japanese Prime Minister Fumio Kishida pledged to strengthen cooperation through consultation, information sharing, and aligned responses to common threats.

Biden hailed progress that the three countries have made since the Camp David summit.

"It's a great group. Fifteen months ago we held the first-ever leader level summit, our three countries at Camp David, back in the United States. And it inaugurated a whole new era of cooperation among our three countries," he said, according to a pool report of the White House press corps.

He added, "I'm proud of how far we've come since that historic meeting -- promoting development in Southeast Asia and the Pacific islands, linking arms to secure the technologies of the future and countering North Korea's dangerous and destabilizing cooperation with Russia."

The outgoing president also expressed his "hope and expectation" that the trilateral relationship is "built to last."

Ishiba echoed the importance of trilateral collaboration in addressing regional challenges, particularly the threats posed by North Korea.

"Although our three countries are facing a highly challenging security environment, our trilateral security cooperation continues to play an essential role in ensuring peace and stability in the Indo-Pacific region," Ishiba said through a translator.

He also welcomed the creation of the trilateral secretariat, saying it would "further strengthen our partnership and enable us to address challenges posed by North Korea and other issues together."

Washington has encouraged Seoul and Tokyo to put aside their historical grievances and deepen bilateral relations in the midst of growing military threats from North Korea, China's increasing assertiveness and other shared challenges.

While questions remain about the future of multilateral cooperation under Trump's second term, Yoon expressed hope that the trilateral framework would continue to receive bipartisan support in the US to address shared security challenges in the region.