Seoul, South Korea – South Korea has announced a finalized agreement with the United States to construct nuclear-powered attack submarines. The White House confirmed its approval for the Republic of Korea (ROK) to build these vessels and committed to cooperation in sourcing the necessary fuel. This development occurs amidst existing geopolitical dynamics on the Korean Peninsula and broader East Asia.
Agreement Details
The submarine agreement follows a broader trade deal reached last month, where the US reduced tariffs on Seoul from 25% to 15%. This reduction occurred after South Korea pledged $350 billion in US investments, comprising $200 billion in cash and $150 billion in shipbuilding.
US President Donald Trump had previously stated on Truth Social that these vessels would be built at a Philadelphia shipyard operated by the South Korean conglomerate Hanwha.
Currently, six nations possess nuclear-powered strategic submarines: the United States, China, Russia, the United Kingdom, France, and India. South Korea's existing fleet comprises approximately 20 diesel-propelled submarines, which necessitate more frequent surfacing compared to nuclear-powered vessels that offer greater range and speed.
Historically, South Korea developed a nuclear weapons program in the 1970s but ceased it under US pressure. Its capacity to enrich or reprocess uranium is presently restricted by the United States, making it reliant on imports for nuclear fuel.
South Korea's Strategic Rationale
South Korea's pursuit of nuclear-powered submarines is aimed at enhancing its defense capabilities in response to North Korea's ongoing nuclear submarine program. President Lee Jae Myung conveyed this objective to President Trump during the APEC summit. South Korea's Minister of Defense, Ahn Gyu-back, stated that these submarines would strengthen the country's defense posture against North Korea.
North Korea's Submarine Program
North Korea is also developing its own nuclear submarine capabilities, potentially with support from Russia. In March 2025, North Korea released images purportedly showing a nuclear-powered submarine under construction, which included a visit by Kim Jong Un to the shipyard. These submarines are anticipated to become operational within the next few years. North Korea is also estimated to possess an arsenal of approximately 50 nuclear weapons.
According to Jo Bee-yun, a research fellow at the Sejong Institute, Seoul's acquisition of nuclear submarines represents a step in East Asia's increasing arms competition, acknowledging North Korea's established nuclear weapon status.
Regional Implications
The impact of nuclear-propelled submarines on South Korea's overall defense capabilities and the balance of power on the Korean Peninsula is a subject of discussion among experts. Yang Uk, a research fellow at the Asan Institute for Policy Studies, suggests that while costly, their primary function is to reassure South Korean voters regarding the government's response to North Korea's nuclear threat, given South Korea's inability to develop its own nuclear weapons. Dr. Yang also indicated that North Korea might interpret this development as a validation for maintaining its nuclear arsenal, potentially complicating future denuclearization efforts.
Conversely, Jo Bee-yun highlighted the strategic advantage for South Korea, describing it as a "major change" that positions South Korea as a "regional player." She noted the speed and range of nuclear submarines would enable South Korea to operate more broadly and cooperate with additional countries.
United States' Perspective
From the US perspective, supporting South Korea's nuclear-powered submarine program is viewed as a means to apply pressure on both North Korea and China. Dr. Yang Uk observed that the US has encouraged South Korea to increase its defense spending, positioning South Korea to potentially act as a proxy in regional pressure dynamics.
The United States and China have historically competed for strategic influence in South Korea. China has recently increased its naval activities near South Korea's maritime border. Following the agreement's announcement, Chinese Ambassador to South Korea Dai Bing urged South Korea to "deal with this issue prudently, taking into consideration the concerns of all sides," and confirmed ongoing diplomatic engagement with Seoul on the matter, emphasizing the "complex and sensitive" security situation on the Korean Peninsula and in the region.