The South Korea sensitive designation, though officially attributed to security violations, reflects deeper concerns over nuclear nonproliferation and threatens U.S.–South Korea nuclear cooperation.
On March 10, the South Korean newspaper*Hankyoreh* reported that the U.S. Department of Energy (DOE) was considering designating Seoul as a “sensitive country.” The next day, South Korean Foreign Minister Cho Tae-yul confirmed that the government was waiting for a response from the DOE and that the designation had not yet been decided. However, on March 14, the DOE confirmed that the country had been added to the Sensitive and Other Designated Countries List (SCL) during the Trump administration’s transition in early January 2025, with the designation taking effect on April 15.
Three days later, the South Korean government announced that the inclusion on the SCL was due to South Korean researchers’ violations of security regulations during their visits to DOE laboratories or participating in joint research projects. In line with Seoul’s explanation, acting U.S. ambassador to South Korea, Joseph Yun said that the designation was a result of “mishandling of sensitive information” rather than a foreign policy decision. So it is “not a big deal.”
This categorization applies to countries forpolicy reasons related to “national security, nuclear nonproliferation, regional instability, threat to national economic security, or terrorism support.” There are twenty-five sensitive countries currently on the list, including American adversaries such as China, Iran, North Korea, and Russia.
Despite Seoul’s inclusion on the SCL, the timing of this designation suggests that Seoul’s ongoing nuclear armament advocacy over the last few years, along with increasing political and security uncertainty, influenced Washington’s decision. Such an inclusion will undermine the country’s high-tech cooperation with the United States, particularly in the nuclear energy industry.
Beyond South Korea’s Designation as a Sensitive Country
Since the end of the Korean War in 1953, both Seoul and Washington have maintained a strong security alliance based on the 1953 Mutual Defense Treaty, which has evolved into a broad strategic partnership with the signing of the 2007 Free Trade Agreement. Reflecting these close ties, the Department of State has never designated Seoul as a “state sponsor of terrorism.”
Given these facts, there is only one reason left for labeling South Korea as a sensitive country: nuclear nonproliferation!
Growing Conservative Support for Nuclear Armament
In early 2023, President Yoon abruptly expressed support for the country’s nuclear weaponization as an option to deter North Korea’s nuclear threat. Subsequently, polls showing strong support for nuclear ambition were released, but their reliability remains questionable. Concerning South Korea’s nuclear proliferation ambitions, then-President Biden persuaded Yoon to dismiss the idea and comply with the Non-Proliferation Treaty (NPT) throughthe Washington Declaration, strengthening extended deterrence.
Contrary to Yoon’s reversed nuclear stance, inconsistencies have often been identified within the government. Cabinet members, such as Defense Minister Kim Yong-hyun and Foreign Minister Cho Tae-yul, have backed nuclear options.
Within South Korean political circles, pro-nuclear sentiment has grown within the conservative ruling party, the People’s Power Party (PPP), which has taken a populist approach. Following a landslide defeat in the National Assembly Election in April 2024 and Yoon’s low approval ratings, PPP members’ nuclear advocacy became noticeable through a series of pro-nuclear policy forums within the National Assembly and key figures’ remarks on nuclear options. Such actions continue while waiting forthe Constitutional Court’s ruling on Yoon’s impeachment after his short-lived martial law last December, potentially leading to an early presidential election.
In response, the main liberal opposition party,the Democratic Party, has firmly opposed the idea of nuclear armament and condemned the PPP for its support of unrealistic nuclear weaponization and Yoon’s martial law, resulting in its inclusion in the SCL.
Political and Security Factors Behind the Designation
Proliferation ambition alone may not have led to South Korea’s listing as a sensitive country. Domestic and economic instability on the Korean Peninsula have significantly played a role.Yonhap News reported that the country was designated as a sensitive country twice, between 1986–87 and 1993–94, based on U.S. Government Accountability Office (GAO) reports.
Following the halt of the 1970s clandestine nuclear program, in the 1980s, North Korea’s threat of a second invasion remained, and South Korea experienced political upheaval after the 1979 military coup and the 1980 Gwangju Democratization Movement. In the early 1990s, the country’s domestic politics stabilized after the June Uprising in 1987, and the two Koreas announced the Joint Declaration on The Denuclearization of the Korean Peninsula. However, North Korea’s resumption of its nuclear program escalated regional insecurity between 1993 and 1994.
Given these previous instances, Yoon’s martial law declaration and North Korea’s growing nuclear arsenals could not be overlooked by Biden in making the decision.
Implications for South Korea’s Nuclear Energy Industry
Once the designation of a sensitive country goes into effect this April,South Korea’s advanced technology fields, such as advanced computing, artificial intelligence, nuclear energy, and quantum technology, are expected to be undermined due to restrictions on joint high-tech collaborations with the United States. For instance, Korean researchers will experience rigorous background checks before visiting U.S. national facilities and research centers.
Among them, South Korea’s civilian nuclear energy industry is vulnerable to its inclusion in the SCL. Following Yoon’s remark in early 2023,Dr. Hecker, the former director of Los Alamos National Laboratory, warned that if the country goes nuclear, it would harm the nuclear export business and domestic nuclear plants’ operations, which aimed to provide 30% of electricity by 2030. Washington can block exports since South Korea’s nuclear technologies are licensed by the United States. In addition to his warning, these proliferation activities could lead to the return of “nuclear material, moderator material, equipment, or component” under Article 17 of theROK-US nuclear energy agreement. The country’s nuclear energy activities could completely cease as a result.
The designation as a sensitive country may not lead to such severe consequences. However, uncertainty remains regarding the scope of restrictions that will be applied to South Korea in both the public and private sectors.
Currently, South Korea needs U.S. cooperation on nuclear energy development. In 2015, both sides renewed the nuclear energy agreement, granting permission for South Korea’s research onpyroprocessing, a type of nuclear reprocessing technology. Beyond the public sector,HD Hyundai and TerraPower recently announced their collaboration to develop commercialized Natrium Reactors, a type of small-scale nuclear reactor. For all these developments, bilateral exchange and collaboration are essential, but their future remains uncertain.
On March 20, South Korean Industry Minister Ahn Duk-geun met U.S. Secretary of Energy Chris Wright in Washington, where both agreed on a swift resolution to remove South Korea’s designation from the list. However, they did not announce whether South Korea would be removed from the SCL before it takes effect on April 15.
Before Minister Ahn’s visit, Choi Jong Kun, former Secretary for Peace and Arms Control under the Moon Jae In administration, underlined in an interview that Seoul’s removal from the list could not be achieved through diplomatic persuasion without the consensus of the DOE, which prioritizes technology safeguards and nonproliferation.
How the Trump Administration Should Respond
Placing South Korea on the sensitive country list was the decision made by the former Biden administration. As a new government seeking to reshape foreign relations, the Trump administration should postpone its effect and reconsider the placement after the political turmoil in its ally subsides.
By including South Korea in the SCL, the United States could risk weakening confidence in the alliance, inadvertently justifying nuclear armament advocates in Seoul, and demonstrating a rift between allies. To maintain the credibility and resilience of the alliance while preserving strategic relations, the Trump administration must carefully assess the broader implications of such an inclusion.
Daeyeon Lee is an international security analyst. He recently graduated from the Middlebury Institute of International Studies with an M.A. 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.
Image: Kampon/Shutterstock.com