Upgrading U.S.-ROK Nuclear Deterrence: The Role of the Nuclear Consultative Group

The Nuclear Consultative Group (NCG) was established following the Washington Declaration in April 2023. Modeled after NATO’s Nuclear Planning Group (NPG), this bilateral nuclear consultative body is designed to enhance deterrence and response capabilities against the North Korean nuclear threat. The NCG meets twice a year to institutionalize policy discussions at the assistant-secretary level on various aspects, including nuclear planning, information-sharing protocols, conventional and nuclear integration exercises, and strategic communication processes during contingencies.

The NCG is undoubtedly an upgrade to the software of extended nuclear deterrence by the United States and the Republic of Korea (ROK). Deterrence depends not only on military hardware—such as strategic assets and force deployments—but also on perceptions of the United States’ willingness to use nuclear forces in defense of South Korea. While the NCG does not fundamentally alter the U.S. nuclear posture, it increases North Korea’s assessment of whether the United States would use nuclear weapons in response to an attack by showcasing U.S. nuclear submarine operations near South Korea. Repeated affirmations by U.S. leaders further reinforce this deterrent effect. At the most recent NCG meeting, the U.S. principal stated that “any nuclear attack by the DPRK against the United States or its allies is unacceptable and will result in the end of that regime” and that “the U.S. commitment to extended deterrence to the ROK is backed by the full range of U.S. capabilities, including nuclear.”

Addressing South Korea’s Dual Fears on Nuclear Deterrence

Although the official goal of the NCG is to deter North Korea, another key policy objective is to reassure South Korea on nuclear matters. South Koreans have two contrasting fears regarding U.S. nuclear deterrence on the Korean Peninsula. One concern is that the existing nuclear capabilities are insufficient to deter North Korea’s nuclear threat. This group of people has consistently demanded more nuclear weapons on South Korean soil, through either redeployment of tactical nuclear weapons or NATO-style nuclear sharing. If neither option is feasible, their logic stretches to advocating for an independent nuclear arsenal. On the opposite side, some South Koreans fear that the United States might use nuclear weapons too aggressively, potentially leading to catastrophic consequences for South Korea, through either precipitous escalation of a crisis or an unnecessary preventive nuclear strike.

The NCG effectively addresses the first concern. One of its most significant policy outcomes has been the increased visibility of U.S. strategic assets on the Korean Peninsula, such as nuclear submarine port calls. Since the NCG’s inaugural meeting, at least three U.S. nuclear submarines have made port calls in Busan. These demonstrations have been welcomed by South Korean conservative elites, who have long sought greater visibility for nuclear assets. While increasing the exposure of nuclear submarines may not be strategically beneficial from a military and deterrence standpoint, these policies effectively mitigate South Korea’s fear about lacking sufficient nuclear assets.

The NCG also seeks to alleviate the second type of fear by ensuring South Korea’s direct participation in decision-making processes and clarifying its role in a nuclear crisis. While this is a meaningful improvement, the NCG should further institutionalize more sophisticated mechanisms for decision-making about the use of nuclear weapons on the Korean Peninsula. For example, it could adopt a framework similar to NATO’s NPG, which might state that a nuclear mission can only be undertaken after explicit political approval is given by the NCG and authorization is received from the U.S. president and South Korean president. The key point is that the NCG should ensure allied political control over decisions about nuclear use, reinforcing the expectation that the interests and safety of South Koreans will be considered in U.S. deliberations on nuclear use.

What’s Next? Opportunities and Policy Options

The NCG is expected to continue and possibly expand during the second Trump administration, as it aligns well with the administration’s two primary foreign policy preferences: adopting a transactional approach to alliances and countering China’s influence. The NCG does not require significant financial or military investment, but it provides a justification and platform for increased South Korean contributions to the alliance. It also strengthens the alliance’s credibility by offering a viable alternative to the ROK’s nuclearization. By keeping South Korea under the United States’ nuclear umbrella with reduced dissatisfaction, the NCG helps maintain U.S. strategic leverage over the country. Moreover, the NCG will become more valuable if Washington seeks to expand the group to include other regional allies like Japan and Australia as part of a broader Indo-Pacific strategy to counter China’s rise.

The U.S. Congress can play an important role in ensuring the long-term success of the NCG. Continued financial support, personnel investment, and interagency coordination will institutionalize the group’s effectiveness. Diplomatic visits and interpersonal engagement by congressional delegations can further bolster the NCG’s objectives by providing additional layers of reassurance to South Korean policymakers. These visits can signal bipartisan support for extended nuclear deterrence and facilitate ongoing dialogue on security commitments. U.S. policymakers should also maintain a clear, consistent message that a nuclear-armed South Korea is not an option. The more South Korean leaders perceive nuclear armament as infeasible, the more they will invest in strengthening mechanisms for extended deterrence.

At the same time, policymakers should ensure that the increased visibility of strategic assets does not result in accidental escalations. Excessive military demonstrations could provoke unexpected reactions by North Korea, exacerbating South Koreans’ security concerns and fueling calls for independent nuclear capabilities. A balanced approach that emphasizes the United States’ commitment to conflict management, de-escalation, and diplomatic engagement will complement deterrence efforts and sustain the alliance’s military preparedness in the long term.

James D. Kim is an Assistant Professor in the Department of Political Science at the University of Washington. He previously was a 2023–24 Stanton Nuclear Security Fellow in the Massachusetts Institute of Technology’s Security Studies Program.