South Korea's Minister of National Defense Shin Won-sik, left, and his U.S. and Japanese counterparts, Lloyd Austin, right, and Minoru Kihara, hold hands after signing a memorandum for the trilateral security cooperation framework at Japan's defense ministry in Tokyo, Sunday. Courtesy of Ministry of National Defense

South Korea, the U.S., and Japan have signed their first formal agreement institutionalizing trilateral security cooperation, aimed at strengthening their joint responses to regional security threats, Seoul's defense ministry announced, Sunday.

The ministry announced that the defense ministers of the three countries — South Korea's Minister of National Defense Shin Won-sik, U.S. Secretary of Defense Lloyd Austin, and Japan's Defense Minister Minoru Kihara — signed the Trilateral Security Cooperation Framework (TSCF) during their meeting at the Ministry of Defense in Tokyo.

The TSCF is the first document jointly signed by the three countries to institutionalize their security cooperation, such as high-level policy consultations, information sharing and trilateral drills, with the goal of providing common policy guidelines to ensure peace and stability on the Korean Peninsula, the Indo-Pacific region and beyond.

While the TSCF is in the form of a memorandum of cooperation (MOC), which is not legally binding, South Korea's defense ministry explained that its purpose is to establish a basis for practical cooperation on more specific matters compared to a memorandum of understanding.

Following the signing, the three countries reaffirmed their commitment to joint security cooperation, vowing to coordinate their responses to regional challenges, provocations and threats, including North Korea's nuclear and missile threats.

"Accordingly, the ministers of the three nations reaffirmed the unwavering nature of the new era of trilateral cooperation," the ministers said in a joint press statement.

The three defense chiefs vowed to enhance cooperation for more effective operation of their real-time sharing of North Korean missile data and will regularly conduct joint drills, including the multidomain Freedom Edge exercise.

The signing of the agreement followed South Korea's initial proposal in February to draft a joint document during a trilateral security meeting. This plan was further refined during the Shangri-la Dialogue in June, where the defense chiefs agreed to finalize the document within the year.

At their first-ever trilateral defense ministers' meeting in Tokyo, the ministers also voiced concerns about the increasing military and economic collaboration between Pyongyang and Moscow. They condemned North Korea's expansion of nuclear delivery systems, its multiple ballistic missile test launches, and other actions that heighten tensions on the Korean Peninsula.

The three ministers will meet in Seoul in 2025 for their next trilateral ministerial meeting.

South Korea's Minister of National Defense Shin Won-sik, right, and his U.S. counterparts, Lloyd Austin, shake hands in Tokyo, Japan, Sunday. Courtesy of Ministry of National Defense

Shin and Austin also held a bilateral meeting, Sunday, addressing various issues concerning the South Korea-U.S. alliance. The two countries reaffirmed their commitment to deterring and responding to North Korean provocations and threats through their combined defense posture and capabilities.

Shin emphasized that North Korea's launches of trash balloons are a clear violation of the 1953 armistice agreement and pose a threat to South Korea's sovereignty. The two Koreas remain technically at war because the fighting in the 1950-53 Korean War ended with a ceasefire agreement and not a formal peace treaty. Both defense ministers strongly urged North Korea to immediately halt these provocative actions.

They also underscored that the mutual alliance is stronger than ever, pledging to continue joint efforts to advance the alliance in order to contribute, not only to peace and stability on the Korean Peninsula, but also in the Indo-Pacific region.

South Korea's Minister of National Defense Shin Won-sik, left, and his Japanese counterpart, Minoru Kihara, shake hands at the Ministry of Defense in Tokyo, Sunday. Yonhap

In a separate meeting with Japan's defense minister earlier in the day, Shin also agreed to enhance bilateral defense exchanges and cooperation, including the resumption of mutual visits between the Army, Navy, and Air Force chiefs of staff and their Japanese counterparts.

It marked the first time in 15 years that a South Korean defense minister visited Japan, and it is the second bilateral meeting this year alone between the defense chiefs of the two countries, following the first one in June.

"As key partners sharing universal values and strategic interests, the two countries will closely communicate on regional and global security issues and continue to strengthen South Korea-Japan ties and the trilateral cooperation based on mutual trust," Seoul's Ministry of National Defense said.