GYEONGJU, South Korea (AP) — President Donald Trump announced via social media on Thursday that the U.S. plans to collaborate with South Korea by sharing advanced technology essential for constructing a nuclear-powered submarine. This revelation followed his discussions with South Korean President Lee Jae Myung.

During their meeting on Wednesday, President Lee emphasized the importance of modernizing the alliance between the U.S. and South Korea. He highlighted the intention to boost military expenditure as a means of alleviating the financial responsibilities on the United States.

President Lee clarified that there may have been some confusion during their previous conversation in August regarding nuclear-powered submarines. He explained that South Korea’s interest lies in acquiring nuclear fuel for submarines, not nuclear weapons.

Lee asserted that equipping South Korea with nuclear-powered submarines could enhance the effectiveness of U.S. operations in the region.

In a separate statement, Trump noted that the construction of South Korea’s nuclear-powered submarine would take place at the Philly Shipyard, which was acquired by South Korea’s Hanwha Group last year.

It was unclear what the size or cost of the sub project would be, but South Korea had said as part of talks with Trump that it had committed $150 billion to invest in America’s shipbuilding capacity.

U.S. nuclear submarine technology is widely regarded as some of the most sensitive and highly guarded technology the military possesses. The U.S. has been incredibly protective of that knowledge, and even a recently announced deal with close allies the United Kingdom and Australia to help the latter acquire nuclear submarine technology doesn’t feature the U.S. directly transferring its knowledge.

Trump’s post on social media comes ahead of his meeting with Chinese President Xi Jinping, whose country possesses nuclear submarines, and after North Korea in March unveiled for the first time a nuclear-powered submarine under construction. It is a weapons system that can pose a major security threat to South Korea and the U.S.

As Trump visited South Korea, North Korea said Wednesday that it conducted successful cruise missile tests, the latest display of its growing military capabilities.

Pentagon officials didn’t immediately respond to questions about Trump’s announcement on sharing the nuclear sub technology with South Korea.

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