Tariff tensions, diverging priorities, and proliferation concerns are stalling US–South Korea nuclear cooperation, testing whether rhetoric can translate into real policy implementation.

South Korea’s National Security Chief Wi Sung-lac recently reported that discussions on strategic security issues—including nuclear-powered submarines, uranium enrichment, and the reprocessing of spent nuclear fuel—have stalled due to the collapse of tariff negotiations with the United States. 

Wi’s remark highlights the current impasse in US-South Korea nuclear energy cooperation, which has yet to move from the discussion stage to actual policy implementation.

On February 14, South Korea’s Foreign Ministry announced that a US delegation—including officials from the National Security Council, the Department of Energy (DOE), the Department of State, and the Department of Defense—would visit Seoul in late February or early March. 

Despite the confidence grounded in the long-standing alliance between the two countries, doubts about South Korea’s commitment to the nonproliferation regime, along with divergent strategic priorities, have contributed to the stalemate over South Korea’s pursuit of sensitive nuclear fuel-cycle capabilities.

APEC Summit and the US-South Korea Joint Fact Sheet 

When South Korean President Lee Jae-myung and US President Donald Trump took office in 2025, they acknowledged the significance of nuclear energy for energy security, particularly in ensuring a stable power supply for future artificial intelligence (AI) data centers.

Both countries possess complementary capabilities. Seoul’s nuclear strengths in Engineering, Procurement, Construction, and Management (EPCM) can support Washington’s plan to expand nuclear capacity to 400 gigawatts by 2050. In return, Washington can contribute to the further development of Seoul’s nuclear energy industry through reactor design expertise, nuclear fuel-cycle technology, patents, and advanced next-generation reactor capabilities. 

Against this backdrop of shared energy security concerns and mutually complementary capabilities, the two leaders discussed nuclear energy cooperation at the Asia-Pacific Economic Cooperation (APEC) summit on October 29, 2025. A month later, their discussions were formalized and documented in the Joint Fact Sheet released in November. The document stated that: “Consistent with the bilateral 123 agreement [US-South Korea nuclear agreement] and subject to US legal requirements, the United States supports the process that will lead to the ROK’s civil uranium enrichment and spent fuel reprocessing for peaceful uses.” 

The prospect of Seoul acquiring uranium enrichment and spent fuel reprocessing capabilities sends a positive signal for the development of its nuclear energy industry; however, uncertainty remains. As reflected in the use of the term “support” rather than “approval,” congressional consent remains an essential requirement for Seoul’s potential acquisition of such sensitive capabilities.

Why Have Further Nuclear Energy Discussions Stalled?

Nuclear energy discussions between South Korea and the United States have stalled for several reasons.

Diverging Strategic Priorities Between South Korea and the United States

President Lee has pursued the acquisition of strategic, sensitive nuclear energy capabilities by sending five high-level government officials to Washington. Between last December and this January, First Vice Minister Park Yoon-joo, Second Vice Minister Kim Gina, National Security Chief Wi Sung-lac, and a representative for Korea-US Nuclear Energy Cooperation Rim Kap-soo successively met with officials from the State Department, Secretary of State Marco Rubio, and Secretary of Energy Chris Wright to discuss the prompt implementation of the Joint Fact Sheet. However, these engagements resulted in no tangible progress.

Meanwhile, President Trump has been prioritizing the restoration of the US nuclear energy industrial ecosystem, which has been weakened over the past several decades. The recent DOE Fact Sheet apparently demonstrates these efforts through initiatives aimed at restoring and expanding the domestic nuclear fuel supply chain, accelerating the development of advanced nuclear reactors, implementing regulatory reforms for nuclear construction, providing large-scale fiscal and financial investments, selecting companies, and launching pilot programs.

In line with these efforts, Secretary of Commerce Howard Lutnick announced last December that of the $350 billion investment pledged by Seoul at the APEC summit, $200 billion would be allocated to nuclear construction in the United States. While legislative procedures were underway in the National Assembly for Seoul’s investment commitments, President Trump unilaterally announced on January 25 an increase in reciprocal tariffs from 15 percent to 25 percent, citing delays in Korea’s investment implementation. 

Rising Concerns about Seoul’s Nuclear Proliferation Commitment

Despite President Lee‘s repeated affirmations of adherence to nuclear nonproliferation, skepticism over Seoul’s nuclear ambitions remains in Washington. A month after the release of the Joint Fact Sheet, President Lee Jae-myung stated that “some within the US government take a cautious stance toward revising the 123 Agreement…I assume that this stance likely reflects concerns about South Korea’s nuclear armament.” Two days later, National Security Chief Wi Sung-lacreaffirmed the President’s concern, underlining the presence of resistance among nonproliferation-focused officials within the Trump administration.

This concern is also apparently noticeable among members of Congress. On January 30, four Democratic senators—including two co-chairs of the Nuclear Weapons and Arms Control Working Group—sent a letter to President Trump, urging him “To Keep Longstanding Ban on South Korean Nuclear Enrichment, Reprocessing,” citing South Korea’s past nuclear ambitions, recent designation of “sensitive country,” and concerns about undermining US nonproliferation efforts. 

Three days later, South Korean Foreign Minister Cho Hyun met with four senators—three Democrats, including Senator Jeff Merkley (D-OR), who had signed the letter a few days earlier, and one Republican. They discussed the prompt execution of the Joint Fact Sheet and South Korea’s commitment to the nonproliferation norm.

Although Minister Cho’s swift engagement with the senators was timely, it remains insufficient to draw bipartisan congressional support for revising the US-South Korea nuclear cooperation agreement. 

What Should South Korea and the United States Do Now?

Separation between Tariff and Nuclear Energy Cooperation

President Trump’s recent remark on a surprising increase in the reciprocal tariffs—from 15 percent to 25 percent—has shaped negative perceptions among South Korean citizens. According to a recent poll, 77 percent supported a cautious stance in response to President Trump’s unilateral statement, viewing it as undermining prior agreements. Furthermore, the US Supreme Court recently struck down Trump’s tariffs. Given these circumstances and uncertainty, the National Assembly may find justification to slow down the legislative process if doing so is deemed to serve South Korea’s national interest. Thus, this nuclear energy cooperation should be handled with care to avoid potential delay in Seoul’s investment.

Prompt Working-Level Discussion

Timely progress in discussions on Seoul’s acquisition of uranium enrichment and spent-fuel reprocessing capabilities is critical to reducing uncertainty about Washington’s commitment. Such progress would not only advance Seoul’s potential acquisition of these capabilities but also support Washington’s nuclear energy renaissance by encouraging Seoul’s investment and strategic participation, thereby providing a foundation for expanded nuclear energy collaboration in reactor construction, small modular reactor (SMR) development, and broader civilian nuclear energy initiatives. 

Seeking Congressional Approval

While doubts within the administration can be resolved through President Trump’s resolve, convincing Congress requires efforts to build confidence in Seoul’s commitment to nonproliferation. Seoul should expand its communication channels beyond individual senators to the Korea–US Parliamentarians’ Union, the Congressional Caucus on Korea, and the Senate Korea Caucus, cultivating bipartisan understanding. In addition, the Trump administration should communicate with Congress, underlining Seoul’s capabilities—financial investment, construction expertise, and human capital—in support of the restoration of the U.S. nuclear energy industry. 

From Political Declaration to Policy Implementation 

The impasse in US-South Korea nuclear energy collaboration reflects misaligned strategic priorities and persistent proliferation concerns surrounding Seoul’s pursuit of sensitive fuel-cycle capabilities. Moving from political declarations to concrete implementation will require separating trade disputes from energy security, initiating immediate working-level engagement, and coordinating sustained efforts to build congressional support.

If the commitments outlined in the Joint Fact Sheet are managed responsibly and implemented effectively, they can become a solid foundation for future strategic nuclear energy cooperation between Seoul and Washington. 

About the Author: Daeyeon Lee 

Daeyeon Lee is an international security analyst. He recently graduated from the Middlebury Institute of International Studies with an MA in Nonproliferation and Terrorism Studies. His research focuses on arms control, nuclear security, the nuclear politics of the Korean Peninsula, and relations between the two Koreas and the United States. He is a junior member of Korea Diplomacy Plaza. Previously, he served as a research associate at the Center for Global Security Research at Lawrence Livermore National Laboratory.

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