The United States has announced plans to share nuclear propulsion technologies with South Korea, marking a significant shift in defense cooperation. President Donald Trump revealed the decision on Wednesday, stating his administration will grant Seoul access to the sensitive technology to enable the construction of at least one nuclear-powered submarine.

This move follows a broader trade agreement between the U.S. and South Korea, which includes a $350 billion investment by Seoul in the American economy. The technology transfer is historic, as the U.S. has previously shared nuclear propulsion know-how only with the United Kingdom and Australia under the 2021 AUKUS pact. Officials cited regional security concerns, particularly China’s military expansion, as a key driver for the decision.

Trump highlighted that South Korea’s nuclear submarine will be built at Hanwha Philly Shipyard, a commercial facility in Pennsylvania acquired by a South Korean company in 2024. The shipyard currently lacks infrastructure to handle nuclear materials or construct military vessels. A statement from Hanwha’s chief strategy officer emphasized the company’s readiness to support the project, citing its advanced shipbuilding capabilities.

In a separate social media post, Trump praised the collaboration, declaring, “South Korea will be building its Nuclear Powered Submarine in the Philadelphia Shipyards, right here in the good ol’ U.S.A.” He also announced plans to resume nuclear weapons testing, stating the move is necessary to maintain parity with rival nations. Trump claimed China’s rapid nuclear advancements could equal U.S. and Russian arsenals within five years, prompting the decision to restart tests.

The president expressed support for “de-nuclearization” but noted discussions with Russia and potential talks with China on the issue.