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The Impact of South Korea’s Construction of Nuclear-Powered Submarines on Inter-Korean Relations and Key Considerations |
| November 10, 2025 |
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Jang Won JoVisiting Research Fellow, Sejong Institute | jjo@sejong.org
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The repercussions of the ROK–U.S. tariff negotiations produced an surprising outcome. As a reciprocal benefit tied to South Korea’s large-scale investment in the United States, the Korean government presented a security bargaining chip during the ROK–U.S. summit, specifically a “request for approval to supply nuclear fuel” required for operating nuclear-powered submarines. In response, President Trump not only agreed to this request but also approved “South Korea’s construction of nuclear-powered submarines.” The significance of this decision extends far beyond the narrow interpretation of merely “enhancing South Korea’s independent defense capabilities.” Grounded in the seventy-year history of the ROK–U.S. alliance, it represents a pivotal turning point that could enable substantial advances in the alliance’s future development.
At the same time, South Korea’s pursuit of “possessing nuclear-powered submarines” is poised to become a central subject of debate, given its potential repercussions for △ inter-Korean relations and China’s relations with North Korea, as well as its intersections with △ the issue of “North Korea’s denuclearization.” This paper examines several security issues surrounding the Korean Peninsula, along with key considerations that warrant careful attention, in the context of what is likely to become a significant “turning point” for inter-Korean relations and the current administration’s foreign policy, namely the pursuit of “South Korea’s possession of nuclear-powered submarines.” -
North Korea has yet to offer any response to the ROK–U.S. announcement regarding South Korea’s nuclear-powered submarines. However, in reaction to the presidential office’s statement that “denuclearization of the Korean Peninsula” would be included as an agenda item for the ROK–China summit during APEC, North Korea issued a Vice Foreign Minister–level statement on October 31 declaring that “denuclearization is nothing but a completely delusional fantasy.”
Following the Russian–Ukrainian war, North Korea’s economic situation has improved more than in past years, largely because of the assistance it received from Russia in return for dispatching North Korean military personnel. In addition, several developments have created one of the most favorable external and internal environments North Korea has experienced in years, such as △ the emerging triangular cooperation structure among North Korea, China, and Russia, △ the inauguration of a new South Korean government that places priority on improving inter-Korean relations, and △ President Trump’s repeated messages indicating his interest in engaging with Kim Jong Un. In light of these developments, the recent announcement of “South Korea’s pursuit of possessing nuclear-powered submarines” has likely prompted North Korea to focus intensively on assessing the potential ramifications and preparing corresponding response measures.
Until news of “the approval of South Korea’s construction of nuclear-powered submarines” emerged during the APEC summit in Gyeongju, conditions had continued to unfold in ways that appeared favorable to Kim Jong Un, with considerable attention focused on whether an impromptu meeting between President Trump and Kim might materialize. During a press briefing aboard Air Force One on October 24, ahead of his tour of Asia, President Trump was asked whether he was willing to accept North Korea’s demand to be recognized as a nuclear-armed state. He responded by stating, “I think they are sort of a nuclear power.” Given that Kim Jong Un had recently asserted △ that North Korea would never abandon its nuclear weapons and that denuclearization was impossible, △ that North Korea should be treated as a nuclear-armed state, and △ that U.S.–North Korea dialogue would be possible only if Washington abandoned its demands for denuclearization, Trump’s remark was interpreted by some observers as a preliminary inducement intended to draw Kim into an impromptu meeting.
Just before attending the APEC summit in Gyeongju, President Trump further signaled his openness to engagement by stating, “If he [Kim] wants to meet, I’d love to,” he said, adding that he “could go over there” while in South Korea, which suggested that he might extend his stay. Although North Korea’s Minister of Foreign Affairs Choe Son Hui criticized the United States during the Minsk International Conference on Eurasian Security on October 27, asserting that “the situation on the Korean Peninsula and in Northeast Asia remains unstable, and various military exercises and actions targeting North Korea, including scenarios for the potential use of nuclear weapons, continue to be observed,” and while North Korea conducted a test launch of a ship-to-surface strategic cruise missile in the West Sea on October 28, some security experts nevertheless anticipated that Kim Jong Un might make a surprise move by accepting President Trump’s proposal for a meeting. Related to this, the National Intelligence Service reported, during the National Assembly Intelligence Committee’s audit of the National Intelligence Service (NIS) on November 4, that “although a potential North Korea–United States summit on the sidelines of APEC did not materialize, various indicators suggest that North Korea has been preparing behind the scenes for potential dialogue with the United States,” adding that “there are some signs that North Korea has analyzed the policy orientations of the working-level officials in the U.S. administration who handle North Korea issues.”
Nonetheless, during the ROK–U.S. summit, the two leaders reaffirmed the principle of “the complete denuclearization of North Korea,” and, in addition to this, the unexpected announcement regarding South Korea’s nuclear-powered submarines extinguished the last remaining spark for an impromptu meeting between President Trump and Kim Jong Un. Faced with this outcome, which ran counter to what North Korea had hoped for, it now confronts the prospect of responding to a “new arms race” that has emerged in ways unfavorable to North Korea. As a result, North Korea is likely to strengthen trilateral military cooperation among North Korea, China, and Russia, while simultaneously preparing military and diplomatic countermeasures directed at the ROK–U.S. alliance.
Consequently, at the time of the current administration’s inauguration, the central priorities of its North Korea policy were △ reducing military tensions and △ improving inter-Korean relations through the restoration of trust, and both Minister of Unification Jeong Dong Young and President Lee Jae Myung had consistently expressed their willingness to resume dialogue with North Korea. However, following the announcement of “South Korea’s pursuit of possessing nuclear-powered submarines” during the APEC ROK–U.S. summit, inter-Korean relations have now entered a phase in which a period of stagnation is likely to persist.
Meanwhile, with regard to President Trump’s announcement approving South Korea’s construction of nuclear-powered submarines, China first expressed its position through the Ministry of Foreign Affairs spokesperson’s regular press briefing on November 1, stating that “both South Korea and the United States must faithfully fulfill their nuclear non-proliferation obligations.” Furthermore, Chinese Foreign Minister Wang Yi, who attended the ROK–China summit on November 1, reportedly remarked on the North Korean nuclear issue that “there have been many changes over time, and since conditions have shifted, a variety of approaches are necessary.”
Even as Beijing has refrained from issuing more explicit statements regarding “South Korea’s construction of nuclear-powered submarines,” Chinese authorities are nevertheless expected to be internally assessing the potential ramifications for regional security dynamics and for China’s own strategic interests, as well as working to formulate corresponding countermeasures.
In the future, South Korea’s possession of nuclear-powered submarines is likely to serve as a significant turning point that could substantially expand the scope of strategic cooperation within the ROK–U.S. alliance. Moreover, if Japan, prompted by South Korea’s acquisition of such submarines, seeks to enhance its maritime capabilities on the basis of the U.S.–Japan alliance, China’s concerns are expected to deepen, given that such developments would markedly strengthen the United States’ maritime security network in Northeast Asia.
As noted above, North Korea’s nuclear and missile development has led to an expansion of United States strategic assets on the Korean Peninsula and has bolstered South Korea’s conventional weapons development capabilities, including the Hyunmoo 5 missile. North Korea’s premature threat to “construct a nuclear-powered submarine” has ultimately produced the unintended outcome of “South Korea’s pursuit of possessing nuclear-powered submarines.” These developments underscore the need to emphasize that North Korea’s ongoing nuclear and missile programs do not produce results advantageous to China. Encouraging this recognition may prompt China, which has long acted as North Korea’s patron, to use this moment as an opportunity to recalibrate its relationship with North Korea. -
In 2025, the international community has continued to invoke the terms “the complete denuclearization of North Korea” and, at times, “the denuclearization of the Korean Peninsula” through △ the ROK–United States–Japan foreign ministers’ meeting, △ the G7 foreign ministers’ meeting, and △ various NATO sessions. However, as evidenced by North Korea’s October 31 statement declaring that “denuclearization is nothing but an utterly delusional fantasy,” North Korea has consistently expressed strong resistance to the use of the term “denuclearization” by South Korea, the United States, and the broader international community. In his policy address to the Supreme People’s Assembly on September 21, Kim Jong Un reiterated this stance by stating, “There can never be any such thing as ‘denuclearization’ for us. We will never abandon our nuclear weapons,” adding that “there would be no reason not to face the United States if it were to give up its obsession with ‘denuclearization.’”
Given the current trajectory of events, the announcement of “South Korea’s pursuit of constructing nuclear-powered submarines through the provision of United States nuclear fuel” has effectively created an opening for China and North Korea to shift from a previously defensive stance on the issue of “North Korea’s (Korean Peninsula) denuclearization” to a more assertive one. This shift is foreseeable because China is likely to contend that, in light of North Korea’s development of △ submarine-launched ballistic missiles and △ efforts to develop nuclear-powered submarines, South Korea’s pursuit of constructing nuclear-powered submarines and the United States provision of enriched uranium fuel amount to actions that run counter to nuclear non-proliferation principles. China is also expected to argue that South Korea “cannot claim exemption from the issue of denuclearization on the Korean Peninsula.”
North Korea stated through a Korean Central News Agency report on December 20, 2018, that the term “denuclearization of the Korean Peninsula” means “the removal of all nuclear threat factors not only within the areas of the North and the South but also from the surrounding region that targets the Korean Peninsula.” It further explained that the only correct definition of “denuclearization of the Korean Peninsula” is “the complete elimination of the United States nuclear threat against the Democratic People’s Republic of Korea.” In line with this interpretation, North Korea is likely to argue that △ South Korea’s construction of nuclear-powered submarines capable of carrying strategic missiles and △ the operational deployment of such submarines using enriched uranium fuel supplied by the United States “constitute violations of the denuclearization of the Korean Peninsula.” If North Korea claims that the Republic of Korea and the United States have “violated ‘denuclearization of the Korean Peninsula,’” and insists that international demands for “North Korea’s (Korean Peninsula) denuclearization” are therefore illegitimate, a prolonged stalemate in denuclearization discussions cannot be ruled out. -
During the ROK–United States summit on October 29, the two leaders reaffirmed the overarching principle of “North Korea’s denuclearization for the establishment of peace on the Korean Peninsula.” In light of this reaffirmation, combined with the subsequent announcement approving South Korea’s construction of nuclear-powered submarines, it has become difficult to expect any dialogue between Kim Jong Un and President Trump before a new turning point emerges next year. It is also assessed that North Korea is likely developing increasingly sophisticated arguments in order to adopt a more assertive position toward the United States and South Korea on issues related to “denuclearization” and “non-proliferation.” Accordingly, South Korea must prepare strategies and measures to counter North Korea’s anticipated offensive. For example, the international community frequently uses the terms “denuclearization of the Korean Peninsula” and “North Korea’s denuclearization” interchangeably. Given that North Korea is expected to claim that South Korea’s pursuit of constructing nuclear-powered submarines, together with the United States support for enriched uranium fuel, “constitutes behavior that violates denuclearization of the Korean Peninsula,” it will be necessary to actively convey to the international community and to policymakers in the United States the importance of using the term “North Korea’s denuclearization” rather than “denuclearization of the Korean Peninsula.”
In the period following the inauguration of the current administration, South Korea adopted an approach to North Korea policy that placed the United States at the center of dialogue efforts, favoring a sequence of “U.S.–North Korea dialogue first ⇒ inter-Korean dialogue later,” and framing the roles as “the United States as peacemaker : South Korea as pacemaker.” Yet, given the current circumstances in which the role of the United States is increasingly constrained, it has become necessary to consider policy options that also make use of China. As noted earlier, North Korea’s nuclear and missile development and its threats regarding the “construction of a nuclear-powered submarine” have ultimately contributed to strengthened South Korean capabilities in conventional weapons development, South Korea’s pursuit of nuclear-powered submarines, and the potential expansion of United States influence around the Korean Peninsula. These developments have placed China in a position of strategic dilemma within the broader dynamics of the peninsula. By framing these dynamics clearly, South Korea may encourage China to restrain North Korea from further arms racing or actions that heighten military tensions and to help facilitate inter-Korean dialogue, thereby contributing to the establishment of peace and stability on the Korean Peninsula. Such considerations point to the need for South Korea to examine how China’s influence can be engaged in a way that supports stability on the Korean Peninsula.
Given that the South Korean government has chosen to pursue nuclear-powered submarines and has obtained U.S. approval for this objective, every effort must now be made to ensure that the goal of “acquiring nuclear-powered submarines” can be realized without disruption. In this regard, President Trump stated that “South Korea’s submarines will be built in the United States.” However, South Korea possesses the infrastructure necessary to produce the critical modules and components of the submarine, including △ the small reactor, △ propulsion control systems, and △ the gearbox. Because South Korean engineers would need to travel between South Korea and the United States to conduct interface testing in order to verify proper assembly and operational functionality, this arrangement would entail substantial economic and time-related costs. Under such conditions, constructing the submarines “in the United States” does not provide a practical environment for carrying out the project. It is therefore essential to actively persuade the United States to allow construction to take place “in South Korea.”
Moreover, for the project to yield tangible results, especially in the context of the fuel supply arrangement, cooperation and understanding from the U.S. working-level officials responsible for regulatory and legislative matters will be indispensable. As this is a long-term project, its continuity must be ensured even if a new administration comes into office and U.S. policymakers or working-level personnel are replaced. To this end, sustained and broad-based support from key U.S. officials and institutions for the “necessity and strategic logic of South Korea’s nuclear-powered submarines” is critical. In this context, proactive outreach by South Korean diplomacy is urgently required.
| Repercussions for Inter-Korean Relations
| The Issue of Denuclearization on the Korean Peninsula
| Considerations for North Korea Policy and the Pursuit of Nuclear-Powered Submarine Construction
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