How a New U.S.-South Korea Deal Can Deter the North Korean Nuclear Threat

In Brief

How a New U.S.-South Korea Deal Can Deter the North Korean Nuclear Threat

The United States and South Korea should pursue an expanded nuclear agreement that supports the production of civilian nuclear power and enhances extended deterrence against the North Korean threat.  

In recent months, North Korean leader Kim Jong-un has threatened to preemptively use nuclear weapons against South Korea and pledged to “exponentially” increase his country’s nuclear arsenal, possibilities that have spooked the South Korean public. President Yoon Suk-yeol mentioned in January that South Korea could develop its own nuclear arsenal or request the redeployment of U.S. tactical nuclear weapons to South Korea. A more effective way of blunting Pyongyang’s efforts to drive a wedge between Washington and Seoul would be for the Yoon and Joe Biden administrations to commit to expanding on the original bargain that underpins U.S.-South Korean nuclear cooperation.

A South Korean woman walks by a TV screen that shows a footage of a North Korean missile launch
A TV screen shows a footage of a North Korean missile launch during a news program at the Yongsan Railway Station in Seoul. Kim Jae-Hwan/SOPA Images/LightRocket/Getty Images

A Test for the U.S.-South Korea Alliance

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Yoon’s comments have roiled the waters around the possibility of South Korea independently developing nuclear weapons capability. Some American and South Korean experts have called on the U.S. government to help South Korea pursue nuclear arms parity with the North, but that has generated strong pushback from American nonproliferation specialists. While the United States and South Korea so far remain officially aligned on nuclear policy, North Korea clearly sees the potential frictions and costs South Korea would generate by pursuing such a path; Pyongyang’s long-standing objective is to break the alliance and peel South Korea away from its reliance on U.S. protection.

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North Korea is keenly aware of the potential economic costs South Korea could incur by violating the Nuclear Nonproliferation Treaty (NPT) and obtaining nuclear weapons; doing so would distance South Korea from the international community and risk severely damaging its export-dependent economy. North Korean authorities would most likely conclude that South Korea’s economic advantages over the North would be reduced if South Korea were to suffer the kind of debilitating international sanctions the North is experiencing.

The Return of Tactical Nuclear Weapons?

The U.S.-South Korean debate over reintroducing tactical nuclear weapons to the peninsula is equally fraught. The United States stationed tactical nuclear weapons in South Korea from the late 1950s to the end of the Cold War. Now, neither the weapons nor the storage facilities are available for redeployment. American nonproliferation specialists also note that stationing tactical nuclear weapons in South Korea would present North Korea with an additional high-value target and that the United States would maintain full control over its nuclear weapons, rather than “share” them with South Korea, no matter where they were stored or deployed.

A recent Center for Strategic and International Studies report on extended deterrence recommended opening bilateral discussions on redeploying U.S. tactical nuclear weapons despite these obstacles. But to some South Koreans, this prospect may feel like an inadequate half-measure, leaving North Korean strategists with a lever through which they can continue to foment dissension between the United States and South Korea.

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Expanding the Nuclear Bargain

The U.S.-South Korea nuclear cooperation agreement, reached in 1974 and revised in 2015, provides a foundation for the countries to increase both peaceful civilian nuclear energy proliferation and nuclear weapons nonproliferation as a means of underscoring the benefits of alliance cooperation in the eyes of the South Korean public.

South Korea relies on nuclear energy for almost 12 percent of its energy consumption needs. Having nearly completed $20 billion in nuclear construction contracts in the United Arab Emirates, the Yoon administration envisions constructing new domestic reactors so nuclear power can fill 30 percent of South Korean energy needs by 2030. It is also bidding for overseas contracts to construct nuclear plants in the Czech Republic, Egypt, Poland, and Turkey.

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Both South Korean and U.S. nuclear energy firms stand to reap substantial gains from an expanded bargain, and they could team up to build civilian nuclear reactors in other regions, which would help those areas diversify energy sources and reduce carbon emissions. Strengthening U.S.-South Korean civilian nuclear cooperation would heighten South Korean awareness of both the tangible commercial benefits of working with the United States and the economic costs of defection from the global nonproliferation regime.

This approach would strengthen the foundations of peaceful U.S.-South Korean nuclear cooperation, underscoring the price South Korea would pay if it pursued weapons development instead. At the same time, Washington and Seoul should strengthen coordination on responses to deter or neutralize possible North Korean nuclear weapons use, regardless of whether the target is San Francisco or Seoul. Revising the Barack Obama­­–era joint Tailored Deterrence Strategy, which outlined steps to discourage North Korean nuclear weapons use, and regularly holding what are known as “table-top exercises” on how to respond to North Korean tactical nuclear use will be important steps. At their November 2022 Security Consultative Meeting, Washington and Seoul agreed to hold such exercises, which typically involve testing their joint ability to plan for and respond to a simulated attack.

This combination of expanded nuclear energy ties and ramped up coordination on how to respond to North Korean nuclear threats offers South Korea and the United States an effective counter to North Korea’s provocations. It can demonstrate that the Washington-Seoul alliance is not vulnerable to such nuclear brinkmanship.

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