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Will Korea really get nuclear-powered submarines?

Published: 14 Nov. 2025, 00:03

Michael Green

The author is the CEO of the U.S. Studies Centre at the University of Sydney and the Henry A. Kissinger Chair at the Center for Strategic and International Studies.

On Oct. 29, President Donald Trump posted on Truth Social that he would give approval for Korea to build nuclear-powered submarines. This would put Korea in the elite club of navies that have this asymmetrical undersea advantage: America, Britain, France, Russia, China, India and soon Australia. The strategic case for nuclear-powered attack submarines is strong. Anything above the water can now be targeted by cruise and ballistic missiles while submarines will remain difficult to detect well into the future, even with advancements in technology, because the undersea domain is a dense web of tides, temperatures and topography. Nuclear powered submarines can hide for months without needing to come up for air, are faster and bigger with more range and firepower than diesel counterparts.

The Virginia-class nuclear-powered submarine USS Missouri is docked at the Busan Naval Base in Busan on Dec. 17, 2023.[NEWS1]

Today most of the major navies of the world are commanded by submariners, and submarine production is the top priority for shipbuilding in the United States, Australia, Japan and Britain. In any future great power conflict at sea, the submarine will be king the way battleships were before aircraft carriers took the throne. And the king of kings will be nuclear powered subs.

But readers should take a deep breath before getting too excited about acquiring this advanced capability. As commanding a presence as Trump can be, a post on Truth Social is not an official U.S. government decision, let alone Congressional approval. I saw up close how challenging it was for Australia to obtain the necessary reforms of export controls, technology transfers and technical capability for Aukus (trilateral security partnership between Australia, the UK and the U.S.) — the arrangement through which the Royal Australian Navy will acquire six Virginia class submarines and then build their own with Britain and the United States in support. Let us take the same hurdles Australia had to overcome and see where Korea is.

U.S. President Donald Trump (L) and South Korea's President Lee Jae Myung take their positions for a photo with other leaders upon their arrival for a special dinner hosted in honor of President Trump and other state leaders at the Hilton Gyeongju hotel in Gyeongju on Oct. 29. [AFP/YONHAP]

First, many commentators are focusing on the U.S.-Korea peaceful nuclear cooperation pact, or the “123” agreement. They identify that as a hurdle because the agreement bans highly enriched uranium in South Korea. Updating the agreement has not always been smooth in the past because of U.S. concerns about nuclear stewardship lapses in some Korean labs. But even if the Trump administration amends the agreement to allow uranium enrichment and convinces the Senate to ratify it, the Korean side will still have to negotiate major changes in U.S. export controls related specifically to nuclear propulsion, and more broadly to ITAR (the International Traffic in Arms Regulations). It took the Australians years to negotiate those legislative changes for Aukus even with a perfect track record of nuclear stewardship and protection of the most sensitive intelligence secrets. In the end, Congress passed sweeping ITAR reforms to allow Aukus to proceed, but with the implicit understanding that Australia would be the last and that the reforms would not be extended to Korea or Japan. Australia also had to pass its own legislation upgrading security of information. Because nuclear-powered submarines are the critical edge for the United States Navy, the ability to release technology will prove far stricter than anything the Korean government or industry have experienced to date. And then there is the question of cost — the Royal Navy and the Royal Australian Navy will likely spend about half their entire navy budgets building, crewing and sustaining their nuclear-powered submarines.

In short, there is an extremely high bar to U.S. assistance for production and delivery of nuclear-powered submarines to the Korean Navy. Nuclear powered subs would also increase the Korean navy’s edge over North Korea's SLBMs. But those incentives will not be nearly enough to get this project over the bar in Washington, particularly if President Trump has to convince a Democratic Congress after 2026.

What would get this project approved is confidence in Washington that Korean navy nuclear powered attack submarines would be part of the region’s collective deterrent against China. But that is a debate Korean governments have not yet had. If governments in Seoul had trouble publicly accepting “strategic flexibility” for U.S. Forces in Korea to be able to operate in Taiwan or other contingencies involving China, will Seoul be ready to introduce nuclear powered submarines with the expectation they will be part of a coalition response to Chinese aggression? Australia faced these same questions and said it could not give a “blank check” to the United States, but U.S. and Australian forces have fought side-by-side in every war since World War I and the Australian forces are built to be ready to do that next time as well. The expectation is that Australia will show up.

Therein lies an irony of the whole debate since Trump’s Truth Social post. Many in Korean industry and media are talking about nuclear powered submarines as if the capability will be handed over and then Korea will achieve greater independence from the United States.

Virginia-class fast attack submarine USS Minnesota (SSN-783) is seen off the coast of Western Australia, Australia March 16, 2025. [REUTERS/YONHAP]

The experience of Britain and Australia was the opposite. The Royal Navy depends heavily on U.S. technology to maintain its nuclear fleet and every U.S. Virginia class attack submarine that leaves Pearl Harbor will soon have Australian crewmen on board. Meanwhile, U.S. nuclear subs will have access to Australian facilities for their own maintenance (the USS Vermont is in Western Australia right now). The belief that Australia will be in the fight made it easier to say yes to transferring nuclear propulsion technology. While the U.S. and Korean militaries have an effective joint and combined posture on the Korean Peninsula (katchi kapshida — “we go together”), they do not in a regional context.

My prediction is that nuclear powered attack submarines will give Korea greater deterrence, prestige and geopolitical influence, but not necessarily more autonomy. The price of admission to the nuclear-powered submarine club will be a more integrated regional and global alliance. I welcome President Trump and President Lee’s enthusiasm about nuclear-powered submarines, but it will not go anywhere until the hard technological, security — and especially geopolitical — questions are considered.