S. Korea, Japan must step up cooperation as US divides focus between Pacific, Middle East: ex-Japanese PM

Former Japanese Prime Minister Shigeru Ishiba delivers a keynote speech during Asan Plenum 2026 at the Grand Hyatt Seoul hotel, Wednesday. The forum is hosted by the Asan Institute for Policy Studies. Yonhap

South Korea and Japan need to strengthen their bilateral security cooperation as the United States' attention remains diverted by its war in the Middle East, former Japanese Prime Minister Shigeru Ishiba said Wednesday.

Speaking at Asan Plenum 2026 in Seoul, Ishiba also said the two East Asian neighbors should take the lead on discussions at the United Nations about the oil supply disruptions at the Strait of Hormuz as part of security measures based on U.N. resolutions.

“Amid an increasingly severe security environment in the Western Pacific, the U.S. continues to face a situation in which it must divide its attention and resources with the Middle East,” Ishiba said at the forum hosted by the Asan Institute for Policy Studies.

The former Japanese prime minister was a keynote speaker at the gathering, which explored new directions for the U.S.-led alliance, under the theme “Modernizing Alliances.”

He described the security environment in the Western Pacific — which includes countries in East Asia, Southeast Asia and Oceania — as “increasingly tense,” pointing to the sight of the leaders of China, Russia and North Korea standing side by side in Tiananmen Square during a Victory Day military parade on Sept. 3, 2025.

The choreographed image symbolized the deepening solidarity of the three Cold War allies, in contrast to the three-way ties among the U.S., South Korea and Japan.

As for the conflict in the Middle East, Ishiba said the blockade of the Strait of Hormuz threatens global peace by interrupting oil transportation. He spoke about two hours after the U.S. and Iran announced a two-week ceasefire.

“Therefore, it should not be addressed through the exercise of self-defense alone, but rather through security measures based on U.N. resolutions, with countries that share the same resolve — including Japan and South Korea — responding in coordination,” he said.

“Wouldn’t it be necessary for Japan and South Korea to jointly take the lead in this discussion at the U.N.?”

Regarding North Korea, Ishiba said deterrence must go beyond the capacity to retaliate against its attacks to include the capacity to prevent damage.

To do so, he said coordination “must be strengthened more rapidly than ever” among the U.S., South Korea and Japan, as well as bilaterally between South Korea and Japan, and between South Korea and the U.S.

On the topic of nuclear sharing, Ishiba pointed to growing discussions in Seoul on nuclear armament and said that coordination in the decision-making process and the associated risks of nuclear weapons is itself meaningful, even if the weapons are not physically deployed.

Concerning a potential contingency in the Taiwan Strait, he warned that the most dangerous scenario would be simultaneous crises on the Korean Peninsula and in the Taiwan Strait, underscoring the need for strategic coordination among allies to prevent such a situation.

On the concept of an Asian-style NATO, Ishiba said that strengthening the “lattice-like” security cooperation among U.S. allies is the most realistic approach.

He said that expanding links among countries such as South Korea, Japan, Australia and the Philippines could serve as the foundation for a future collective security system.

The former Japanese leader attended a luncheon later in the day with President Lee Jae Myung at Cheong Wa Dae in Seoul.

Ishiba held office as prime minister for about a year until October 2025. During that time, he met with Lee three times for summits and contributed to resuming reciprocal visits between the two countries' leaderships.