Japanese Foreign Minister Iwaya Takeshi (left), U.S. Secretary of State Marco Rubio (center), and South Korean Vice Foreign Minister Park Yoonjoo meet on the sidelines of the ASEAN Summit on July 11. (©MOFA Japan)
Facing a deteriorating security environment in East Asia, Japan, the United States, and South Korea are working to strengthen trilateral cooperation.
That commitment was on display at two high-level gatherings on July 11. One in Kuala Lumpur during the ASEAN Foreign Ministers' Meetings, and the other in Seoul among top military officials. At both venues, representatives from the three countries reaffirmed their resolve to confront shared regional threats.
Yet even as they recommit to regional security, renewed US tariff threats and looming defense burden-sharing talks risk complicating those efforts and rekindling doubts over long-term alignment.
Trilateral Coordination
In Kuala Lumpur on Friday, Japanese Foreign Minister Takeshi Iwaya met with US Secretary of State Marco Rubio and South Korean First Vice Foreign Minister Park Yoonjoo. The senior officials expressed concern about North Korea's advancing nuclear and missile capabilities and reiterated their commitment to East Asia's stability.
They also pledged closer coordination on a range of security challenges, including the deepening Russia–North Korea ties and Pyongyang's cyber activities, particularly cryptocurrency thefts that help fund its weapons programs.
That same day in Seoul, military heads from the three countries gathered for the 22nd Trilateral Chiefs of Defense meeting. Chairman of the US Joint Chiefs of Staff Dan Caine commented that both North Korea and China were undergoing an "unprecedented military buildup" with "a clear and unambiguous intent to move forward with their own agendas."
He stressed that wider integration was necessary to restore regional deterrence. "We need to be able to demonstrate resolve, to be entrepreneurial and proactive in our partnerships," Gen. Caine said.
In recent years, Washington has pushed to expand the US–Japan–South Korea security partnership beyond North Korea to address growing Indo-Pacific risks, especially from China.
Tariffs Test the Alliance
But this strategic vision is unfolding at an awkward moment. Four days before the public show of unity, President Donald Trump revealed plans to impose a 25% tariff on all imports from Japan and South Korea. This comes on top of a baseline 10% rate and sector-specific tariffs already imposed on two of Washington's closest allies.
The reaction in Tokyo was swift. Speaking during a campaign stop on Wednesday, Prime Minister Shigeru Ishiba made a rare show of defiance. "Do not look down on us," he said. "We will protect what must be protected" in negotiations over the tariffs.
It's uncommon for a Japanese leader to address frictions with Washington in such strong language, even ahead of a critical domestic election.
Meanwhile, in South Korea, there is growing speculation that officials may be considering their own leverage. While National Security Adviser Wi Sung-rak recently denied the reports, some believe Seoul's left-wing government is weighing the return of wartime operational control (OPCON) as a potential bargaining chip.
The idea is to link an increased defense burden with greater military autonomy and, in turn, leverage that position in pursuit of tariff relief.
Soft-Pedaling on Beijing
Unlike their predecessors, Prime Minister Ishiba and South Korean President Lee Jae-myung have signaled a more conciliatory approach toward Beijing, and their strategic divergence is beginning to show.
The joint statement issued after the Seoul defense summit omitted any mention of China, despite early talks of identifying it as a rising security threat. According to diplomatic sources, the exclusion was likely made to reflect Seoul's desire to avoid antagonizing Beijing directly.
That same hesitancy is also playing out in the domestic arena. On July 3, South Korea's National Assembly passed a resolution condemning China's installation of steel structures in the West Sea, within Korea's Exclusive Economic Zone. Though it passed 252 to 0, seven lawmakers, including three from Lee's ruling party, abstained.
Japan, too, is moving cautiously. Though Ishiba has reiterated his support for the US alliance, his tone on China has been noticeably softer than his conservative predecessors.
In June, when a China Coast Guard vessel and helicopter violated Japanese territorial waters and airspace near the disputed Senkaku Islands, Ishiba refrained from issuing a formal condemnation. A similar trend has been evident as Chinese aircraft have been maneuvering increasingly recklessly around Japanese planes.
Uneasy Alignments
All of this comes as the US is pressing its two closest regional allies to expand their roles in collective security in efforts to contain China.
Experts argue that as Trump's economic pressure and defense cost-sharing disputes reignite tensions, the window for stronger tripartite cooperation could narrow, potentially pushing Seoul and Tokyo closer to Beijing's orbit.
With North Korea accelerating its weapons program, China's expanding maritime assertiveness, and Moscow's deepening ties with Pyongyang, the Indo-Pacific faces heightening volatility, exactly when harmony among US allies is most needed.
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Author: Kenji Yoshida
