US Clears Nuclear-Powered Attack Submarines for South Korea — What It Means for the Region

US and South Korea Finalise Nuclear-Submarine Agreement

The United States has approved a plan for South Korea to develop nuclear-powered attack submarines and will cooperate on identifying sources of nuclear fuel, the White House said in a fact sheet released on Thursday. The move deepens security cooperation between Washington and Seoul amid rising tensions on the Korean Peninsula and increased naval activity by China in nearby waters.

Background and trade linkage

The announcement follows a broader bilateral package agreed last month that reduces reciprocal tariffs from 25% to 15%. South Korea’s pledge of significant investment in the US — and related shipbuilding commitments — helped smooth negotiations. US President Donald Trump also posted on Truth Social indicating the vessels would be constructed at a shipyard in Philadelphia reportedly owned by South Korean conglomerate Hanwha, though South Korean officials have said domestic yards are better positioned to deliver on schedule.

What nuclear propulsion delivers

Currently only a handful of countries operate nuclear-powered strategic submarines — the United States, China, Russia, the United Kingdom, France and India. South Korea operates roughly 20 diesel-electric submarines today; nuclear propulsion would give future boats greater range, higher sustained speeds and much longer submerged endurance, improving patrol reach and stealth.

Security rationale and regional response

Seoul frames the programme primarily as a response to North Korea’s growing undersea capabilities. Pyongyang has released images of a submarine it says is nuclear-powered and analysts suggest it could field such vessels within a few years. North Korea is also estimated to possess an arsenal of roughly 50 nuclear warheads as part of its wider weapons programme.

Ahn Gyu-back, South Korea’s defence minister: "Nuclear submarines would be a proud achievement and a major leap in strengthening defence against the North."

Analysts offer mixed views. Jo Bee-yun of the Sejong Institute says the boats will help Seoul keep pace in East Asia’s intensifying arms competition, noting the strategic advantages of speed and range. Yang Uk of the Asan Institute cautions that while the submarines are politically reassuring for South Korean voters, they are costly and may not decisively shift the balance of power on the peninsula.

Diplomatic and non-proliferation considerations

Because South Korea’s civilian nuclear activities are governed by agreements with the United States, the new submarine programme requires amendments to bilateral nuclear cooperation arrangements so the US can provide fuel and define limits on military use. Washington will likely attach safeguards and operational conditions to any fuel supply and technical cooperation.

China has expressed concern. Beijing's ambassador to Seoul urged prudence and warned the security situation in the region remains "complex and sensitive." Experts say the agreement will complicate Seoul’s diplomatic balancing act between Washington and Beijing.

Construction, costs and timeline

Officials disagree about where the boats should be built. While the US president suggested a Philadelphia shipyard, South Korean leaders and some reports argue domestic yards have greater capacity to build the submarines more quickly. Building and operating nuclear-powered submarines is expensive and technically demanding; delivery schedules, cost-sharing and industrial arrangements remain key unresolved issues.

Next steps

The practical follow-up will include negotiating changes to the nuclear cooperation pact to permit US fuel transfers, setting non-proliferation safeguards and finalising technical requirements, industrial plans and timelines for construction. The agreement marks an important strategic step for Seoul and Washington, but many operational, diplomatic and budgetary questions remain.