Trump Announces U.S. to Share Nuclear Submarine Technology with South Korea After Meeting President Lee Jae Myung

The United States will share closely guarded technology to help South Korea build a nuclear-powered submarine, President Donald Trump announced Thursday on social media, following his meeting with South Korean President Lee Jae Myung.

During their talks on Wednesday, President Lee emphasized his desire to modernize the U.S.–South Korea alliance, pledging to increase Seoul’s defense spending to ease America’s financial burden in maintaining regional security.

Lee clarified that South Korea’s interest in nuclear-powered submarines was focused on nuclear fuel, not weapons, addressing what he called a previous “misunderstanding” from their August discussion. He explained that Seoul’s current diesel-powered submarines are limited in their ability to track and shadow other nations’ underwater operations. Nuclear-powered submarines, by contrast, can remain submerged for extended periods, offering far greater range and stealth.

Trump added in a separate post that the new submarine would be built at the Philly Shipyard, which was acquired last year by South Korea’s Hanwha Group. While details about the project’s size or cost remain unclear, South Korea reportedly committed $150 billion to boost America’s shipbuilding capacity as part of broader defense cooperation.

The move represents a major shift, as U.S. nuclear submarine technology is among the most tightly guarded in the world. Washington has historically been extremely cautious about sharing it — even the AUKUS pact with close allies Australia and the United Kingdom stops short of a full technology transfer.

Trump’s announcement comes ahead of his expected meeting with Chinese President Xi Jinping, whose country already operates nuclear-powered submarines. It also follows North Korea’s recent unveiling of its own nuclear-powered submarine under construction — a development seen as a potential threat to both South Korea and the U.S.

As Trump toured South Korea, North Korea claimed it successfully tested new cruise missiles, underscoring rising military tensions in the region.

Officials at the Pentagon have yet to comment on Trump’s statement or provide clarification on whether the U.S. military will formally proceed with transferring such sensitive technology to South Korea.