AJP Focus: Seoul's nuclear submarine push raises broader regional security questions

By Kim Hee-su Posted : May 27, 2026, 17:53 Updated : May 27, 2026, 17:56
President Lee Jae Myung (center) attends a meeting in Jinhae, South Gyeongsang Province on May 26, 2026. Yonhap
SEOUL, May 27 (AJP) - South Korea's new "Jangbogo N" nuclear-powered submarine program is raising questions over whether the project is designed primarily to deter North Korea or whether it could eventually become part of a broader U.S.-led effort to counter China.

Officials have described the submarine as a symbol of Seoul's determination to take greater responsibility for its own security. But the move comes after the commander of U.S. Forces Korea recently described South Korea as a "dagger" from China's strategic perspective.

Under the current timetable, the first vessel is expected to become operational in the mid-2030s.
 
Defense Minister Ahn Gyu-back presents a basic plan for developing nuclear-powered submarines during a meeting chaired by President Lee Jae Myung in Jinhae, Changwon, South Gyeongsang Province, May 26, 2026. Yonhap
Defense Minister Ahn Gyu-back unveiled the plan during the first meeting of the Future Defense Strategy Committee at the Navy Submarine Command in Jinhae on Tuesday.

"The nuclear-powered submarine, to be built on the foundation of a strong South Korea-U.S. alliance, will be a symbol of our will to take responsibility for peace and security on the Korean Peninsula ourselves," he said.

Ahn added that the project would also contribute to strengthening South Korea's defense industry and play a key role in countering North Korea's submarine-based nuclear and missile threats.

According to the Defense Ministry, the submarine South Korea plans to build will carry conventional weapons and is unrelated to strategic nuclear submarines armed with nuclear weapons. Its reactor will use low-enriched uranium at around 20 percent, rather than highly enriched uranium that can be used to produce nuclear weapons.

The U.S. currently uses highly enriched uranium of more than 90 percent for its nuclear submarines, while France and China are known to operate nuclear-powered submarines based on low-enriched uranium.
 
U.S. Forces Korea Commander Gen. Xavier Brunson speaks at a U.S. House Armed Services Committee hearing in Washington, D.C. on April 9, 2026. Courtesy of the U.S. House Armed Services Committee
Under the South Korea-U.S. nuclear cooperation agreement signed in 2015, Seoul requires Washington's consent to enrich uranium below 20 percent and reprocess spent nuclear fuel. South Korea has so far been effectively unable to enrich uranium and imports all nuclear fuel used in its power plants.

If Seoul seeks to receive nuclear fuel for its submarines from Washington, the two countries will need further discussions, including a separate agreement under the U.S. Atomic Energy Act. Any transfer of nuclear fuel would also require approval from the U.S. Congress.

The plan comes as the second Trump administration, under its "Make America Great Again" agenda, presses allies to invest more in their own defense and assume a greater share of collective security responsibilities.

South Korea is also facing growing pressure as the U.S. war with Iran drags on. Washington has called on Seoul, where about 28,500 U.S. troops are stationed, to contribute more to U.S.-led security efforts, while President Lee Jae Myung has emphasized the need for greater defense self-reliance.

According to the U.S. Army War College website on Tuesday, Gen. Xavier Brunson, commander of U.S. Forces Korea, said during a podcast hosted by the school on May 22 that, from China's perspective, "what they see is Korea, a dagger in the heart of Asia, and Japan, which is kind of the shield or the blocking wall as they have ambitions to get beyond the South China Sea."
 
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Experts say the Jangbogo N program is not merely a matter of strengthening military capabilities, but a strategic decision about how South Korea will acquire and operate nuclear-powered submarines.

They note that the issue has become more complex amid the AUKUS pact and intensifying U.S.-China maritime competition. Seoul must pursue domestic shipbuilding capabilities while complying with the global nonproliferation regime, even as its new submarines are likely to be viewed by Beijing as part of a wider effort to check China's growing naval reach.

Because nuclear-powered submarines can operate for more than 40 years, heavy dependence on foreign technology or components in the first vessel could lock Seoul into long-term reliance on outside support for maintenance and upgrades.

Jeong Kyung-woon of the Korea Association of Military Studies said in a report that the SSN project is "not a one-time purchase, but a structural choice that will define South Korea’s future submarine force," adding that the level of domestic shipbuilding and defense industry involvement from the initial stage will determine the country's technological autonomy and long-term cost curve.

Still, the government appears to be leaving room for further consultations with Washington over where the submarines will be built. President Donald Trump wrote on Truth Social the day after the Oct. 30 summit that South Korea would build its nuclear-powered submarines "right here in the good ol' U.S.A. shipyards of Philadelphia.” The South Korean government, however, has since made clear that it intends to build them domestically.

Analysts also warn that while SSNs could eventually be drawn into long-range missions aimed at countering China, Seoul should clearly define their primary role as deterring North Korea.

"South Korea already has enough strategic requirements within its exclusive economic zone and surrounding waters," Jeong added. "If Seoul openly expands the mission of its nuclear-powered submarines to counter China, it could invite responses from the Chinese and Russian navies and fuel a regional arms race."

Experts said that the more deeply South Korean SSNs are integrated into U.S.-Japan combined operational networks, the more likely China is to view them as forward-deployed U.S. offensive assets — much as it viewed the THAAD missile defense system, elements of which have reportedly been redeployed from Korea to the Middle East amid the prolonged war with Iran.

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