What does the Korea-US nuclear submarine deal mean?

The Korean government announced that it has finalized an agreement on building nuclear-powered submarines in cooperation with the United States.

The United States has approved “attack submarines” and agreed to cooperate on fuel procurement, according to a release from the White House on Thursday.

The agreement marks a significant step forward in relations between South Korea and the United States and comes at a time of heightened tensions on the Korean Peninsula due to nuclear-armed North Korea and Western expansionist China.

Here’s what you need to know about contracts:

The agreement between the U.S. and South Korea comes as the leaders of the two countries reached a broad trade deal early last month that would cut mutual tariffs from 25% to 15%.

US President Donald Trump imposed a 25% tariff on South Korea earlier this year, but Vice President Lee Jae-myung successfully negotiated a rate lowering it to 15% after the Korean government said it would invest $350 billion (£265 billion) in the US, including $200 billion in cash investment and $150 billion in shipbuilding.

A White House report released Thursday said the United States “has approved South Korea’s construction of a nuclear-powered attack submarine… and will work closely to advance the requirements of this project, including fueling methods.”

President Trump previously announced in a post on his social media platform, Truth Social, that the ship would be built at a Philadelphia shipyard operated by South Korean conglomerate Hanwha.

Currently, only six countries possess nuclear-powered strategic submarines: the United States, China, Russia, the United Kingdom, France, and India.

South Korea already has about 20 submarines, but they are all diesel-powered and will need to surface much more frequently. Nuclear submarines can also operate farther and faster.

“I have authorized them to build nuclear-powered submarines instead of the outdated and much less agile diesel-powered submarines they have now,” Trump wrote on Truth Social.

Korea is a powerhouse in the civil nuclear energy sector. It had a nuclear weapons program in the 1970s, but abandoned it under pressure from the United States.

Therefore, because we are entirely dependent on imports of uranium, our ability to enrich or reprocess uranium is limited by the United States.

The latest ship program is aimed at countering North Korea, which recently said it was pursuing its own nuclear submarine program.

President Lee told Trump at the APEC summit last month that South Korea was needed for that explicit purpose.

In a TV interview last week, South Korean Defense Minister Ahn Gyu-baek said the nuclear submarine would be a “proud achievement” for South Korea and a big step forward in strengthening its defenses against North Korea.

He added that the nuclear submarine’s stealth capabilities would keep North Korean leader Kim Jong-un “up at night.”

North Korea has also been pursuing a nuclear submarine program, possibly with help from Russia, according to South Korean officials.

In March 2025, North Korea released photos showing what it claimed was a nuclear-powered submarine under construction, showing Chairman Kim visiting a shipyard.

North Korea is expected to have submarines within the next few years.

North Korea is also believed to have about 50 nuclear weapons as part of its broader nuclear weapons program.

Cho Bi-yoon, a researcher at the Sejong Institute, suggested that South Korea’s acquisition of nuclear submarines would help keep pace with the increasingly intensifying arms race in East Asia.

“North Korea’s nuclear weapons are an established fact,” she said in an interview with the BBC. “(South Korea’s) acquisition of nuclear submarines is just one step in a larger trend of increasing tensions.”

It’s unclear how much nuclear-powered submarines will contribute to South Korea’s defense capabilities, and while they are very expensive, they won’t significantly change the balance of power on the Korean Peninsula, according to some experts.

Yang Wook, a researcher at the Asan Institute for Policy Studies, told the BBC that the main purpose of the nuclear submarine was to reassure South Korean voters that the government was responding to North Korea’s nuclear threat.

“South Korea cannot develop its own nuclear weapons to counter North Korea,” said Dr. Yang. “What can they do? Deploy nuclear submarines.”

Dr. Yang believes North Korea may enjoy the change because it strengthens its legitimacy for having nuclear weapons. This means it will be more difficult to demand that North Korea give up its nuclear weapons.

Nonetheless, Minister Cho emphasized the strategic advantages South Korea could gain from the new submarine deal, describing it as a “massive change” that “means South Korea is now a regional player.”

“The best characteristic of a nuclear submarine is speed,” she said. “Now we can go faster and farther, and Korea can cooperate with more countries.”

For Washington, support for South Korea’s nuclear-powered submarine program is likely aimed at putting pressure on both North Korea and China.

Dr. Yang explained, “President Trump passed the burden of defense spending on to Korea.” “South Korea will significantly expand its defense budget. South Korea will act as a proxy for the United States in pressuring China and North Korea.”

The United States and China have long competed for strategic influence in Korea, forcing South Korea to walk a geopolitical tightrope. Recently, China has been increasing its naval activities near the Korean maritime border, a move similar to that seen in the South China Sea.

Dr. Yang said China may be “angry” about the nuclear submarine agreement between South Korea and the United States.

“I hope South Korea will deal with this issue carefully, taking into account the concerns of all parties,” Chinese Ambassador to South Korea Dai Bing said after the agreement was announced.

Prime Minister Dai also added that China is communicating with South Korea through diplomatic channels on this issue and emphasized that “the (security) situation on the Korean Peninsula and in the region remains complex and sensitive.”

President Trump said the submarines would be built in Philadelphia and bring jobs to the United States, but South Korean officials insisted they be built locally so existing facilities could deliver the submarines on a much shorter schedule.

South Korea’s Prime Minister Kim Min-seok reportedly said directly during a National Assembly hearing that the South Korean-owned Philadelphia shipyard “does not have the capacity” to build such ships.

Hanwha, which owns the shipyard, has not yet revealed its position on this.

But now that an agreement has been reached, the next step is to coordinate a nuclear deal between the two countries that would allow the United States to provide nuclear fuel and hedge its military use.