South Korea’s Asia-Pacific Economic Cooperation (APEC) summit showcased a tightening defense partnership with the United States. The U.S. push for allies to shoulder greater security burdens converged with South Korean efforts to deepen autonomy and prepare for long-term uncertainty about U.S. commitments, creating a mix of deeper operational integration and quiet hedging.
The Trump administration, under the umbrella of “alliance modernization,” is pushing for increased South Korean defense spending and a shift in U.S. focus from solely countering North Korea to “strategic flexibility,” which would allow U.S. forces in South Korea to assume regional missions aimed mainly at China. South Korea is expanding defense investment, accelerating transfer of wartime operational control (OPCON), and pursuing nuclear fuel capabilities, all while reiterating that it will not be dragged into a broader confrontation with China.
The upshot is a more capable, forward-leaning alliance that is also more transactional, competitive, and sovereignty-driven. The question for policymakers is whether this becomes the new normal of the alliance or the first phase of a more fragmented Indo-Pacific.
Another Layer
A similar tightening of ties occurred in parallel between President Donald Trump and new Japanese Prime Minister Sanae Takaichi, as well as her surprisingly warm meeting with Korean President Lee Jae Myung on the sidelines of APEC. Beneath this official narrative of drawing closer, however, there is another layer to security developments.
“Both Korea and Japan are trying to keep the Americans locked in while they are preparing for the day when America doesn’t care enough to protect you,” says a Seoul-based observer familiar with the thinking of both Korean and Japanese senior officials, who preferred to comment on background. “The trade and investment deal components of this are ultimately protection money,” he added. “They wouldn’t be doing it if there wasn’t the risk of losing security guarantees from the U.S.”
The trade pressures may reinforce the need to tighten security ties, but they also undermine confidence in the alliance, some experts believe.
“U.S. expressions of support for allies are in the context of helping them to assist the U.S. coalition against China,” says Bruce Klingner, senior fellow at the Maureen and Mike Mansfield Foundation and former CIA analyst. “Yet, that effort is undermined by Trump’s arbitrary, protectionist tariffs, which pummeled allies worse than opponents.
The United States, Klingner added, forced South Korea “into a disadvantageous trade deal” that violates the U.S.-South Korea free trade agreement (KORUS FTA).
Nuclear Submarines?
The centerpiece of an apparent new level of U.S.-South Korea security cooperation is an agreement for joint production of nuclear-powered submarines at a South Korean-owned shipyard in Philadelphia.
“South Korea will be building its Nuclear Powered Submarine in the Philadelphia Shipyards, right here in the good ol’ U.S.A.,” Trump proclaimed in a October 29 post on Truth Social. “Shipbuilding in our Country will soon be making a BIG COMEBACK.”
Some experts claimed this was a breakthrough toward strategic interdependence.
“This move dismantles the old anmi-gyeongjung (security with the United States, economy with China) framework,” wrote Seong-Hyon Lee, a senior fellow at the George H.W. Bush Foundation for U.S.-China Relations, in The Interpreter. “South Korea is no longer merely buying American security; it is integrating its industrial base with that of the United States to form a single, strategic-economic bloc,” argued Lee.
But subsequent developments call this into question. Senior executives at Hanwha, the South Korean firm that has taken ownership of the Philly Shipyard, admitted that the facility is not capable of building a nuclear-powered submarine, not only technically but also because of insufficient security to conduct such secret work.
Senior South Korean officials have since told the National Assembly that the intention is, in fact, to build those submarines in South Korea, with the clear goal of enhancing the country’s defense capabilities, independently of the United States.
“Investing in a submarine facility at the Hanwha Philly Shipyard would not be realistic, and neither would it be realistic to contract with an American company like General Dynamics to build the submarines,” National Security Advisor Wi Sung-lac told the National Assembly’s House Steering Committee. While paying due respect to the alliance, “we’re emphasizing defense autonomy as we seek to take on a bigger role and make greater contributions,” Wi said.
The Greater Prize
Behind the nuclear submarine agreement lies a deeper, and more significant, agenda for the Lee administration: a revision of the civilian nuclear cooperation agreement, known as the 123 Agreement, to give South Korea the ability to enrich nuclear fuel and reprocess spent fuel, both of which are important to the expansion of the country’s nuclear power industry but also needed to operate submarine reactors. While the submarine agreement has gotten most of the media attention, the 123 Agreement’s revision is the greater prize.
South Korea has long sought this goal but has been blocked by the United States, which saw this as a doorway to potential nuclear weapons proliferation. By framing this as an issue of civilian nuclear power development, however, South Koreans in both conservative and progressive camps saw this as a means of acquiring near-threshold capability to go nuclear, without yet crossing the line—what some refer to as nuclear latency.
South Korean officials, in this view, understood that an appeal to build their nuclear power industry was not going to appeal to President Trump and his senior officials. But it could gain support if packaged as part of taking more responsibility for their own defense.
“Mr. Trump either did not understand the implications, or did not care,” wrote The Economist. “South Korea’s moves toward an insurance policy betray great unease about the future of its alliance with America.”
If the president did not understand what he signed off on in Seoul, national security officials in Washington with long experience on these issues are apparently aware of the Pandora’s box that was being opened. According to Korean media reports, the delay in publishing a written joint document detailing the agreements reached on tariffs and national security issues is due to an internal review in Washington.
A senior official in the South Korean government told the Hankyoreh newspaper that “the US Department of Energy is apparently upset with how many concessions Korea received in regard to the two countries’ nuclear energy agreement.”
OPCON transfer and the China question
The delay in issuing a joint statement following the Security Consultative Meeting between U.S. Secretary of Defense Pete Hegseth and South Korean Minister of National Defense Ahn Gyu-back, along with senior officials, may have partly been due to a lack of detailed agreement on key issues.
The two sides discussed the transfer of wartime OPCON, based on a previous plan that set out three phases to verify the operational capabilities of a future Combined Forces Command under a South Korean commander. The transfer has been stalled due to delays in U.S. verification and the lack of urgency by the previous conservative government.
In the joint meeting and in a direct meeting between Hegseth and Lee, the South Korean leader expressed his desire to complete the second phase by 2026 and move rapidly toward finalizing the transfer. Lee pitched this as a gesture toward the Trump administration’s expressed desire to shift its defense role.
“The early recovery of wartime operational control within my term will be an important opportunity to further deepen and develop the South Korea-U.S. alliance,” Lee reportedly told Hegseth. “If our military capabilities are significantly strengthened and we take the lead in defending the Korean Peninsula, the U.S. defense burden in the Indo-Pacific region will also be reduced.”
Hegseth made no specific commitments on concluding the verification process on South Korea’s desired timetable. There was similar ambiguity on the issue of “strategic flexibility,” an issue that has long been discussed between the two allies. The term refers to the idea that U.S. forces based in South Korea might be deployed out of the peninsula for missions other than the defense against North Korean aggression.
The two sides have sidestepped this issue by agreeing in general terms that U.S. forces can be moved wherever the U.S. commander-in-chief wants, while retaining the understanding that those forces are there to defend South Korea against a North Korean attack. South Korea has long insisted that the 28,500 U.S. forces based in South Korea are essential for the defense against a potential North Korean attack, but also as the trigger for deploying massive U.S. forces committed under joint operational plans.
Behind this issue lies South Korean concerns that the Trump administration might seek a peace deal with North Korea that could lead to the withdrawal of U.S. forces from South Korea. Hegseth and senior U.S. military officials have pledged to maintain the force commitment in South Korea. But he also alluded to their use in contingencies beyond the Korean Peninsula, most likely around Taiwan.
“At the same time, we need to enhance flexibility to respond to other contingencies in the region,” Hegseth said following the security talks. He called for deeper coordination between the two countries to expand the strategic flexibility of U.S. Forces Korea (USFK).
South Korea, however, is not committed to a wider confrontation with China. Lee, while shoring up ties with the United States, has cultivated closer relations with China, particularly in the realm of economic cooperation. The APEC sideline meeting between Lee and Chinese leader Xi Jinping reportedly featured extensive discussions and personal warmth. It was notably different in tone from the brief thirty-minute meeting between Xi and Takaichi, which was clearly frosty.
“There will be disagreement between the U.S. and South Korea on China policy, but a greater similarity of views on North Korea because both Trump and Lee want to engage North Korea,” observes Klingner. “On China, Lee will still try to straddle the fence.” The meeting with Xi focused on the restoration of economic relations and a plea to Xi to encourage North Korea to resume engagement.
The goal of pairing security ties with the United States and economic ties with China has been a consistent feature of South Korean foreign policy, including under the previous conservative Yoon Suk Yeol administration, which was also careful about offering overt support for military contingencies around Taiwan.
“As the role of U.S. Forces Korea expands, it is crucial to establish safeguards through sufficient consultation to ensure that South Korea is not drawn into regional conflicts against its will,” Donga Ilbo commented.
Multilayered Policy
The effort by South Korean leaders to balance the competing demands of their ally, the United States, and the pursuit of national interests in Northeast Asia is not new. The goal of greater defense self-reliance has also been long-standing, particularly by progressive South Korean administrations. The difference now lies mostly in the volatile nature of the Trump administration and uncertainty about its policy direction. That drives South Korea and Japan, and other U.S. allies, to increasingly think about lessening dependency on the United States.
“Unpredictability makes everyone nervous, and it leads them to consider other alternatives,” says Klingner.
