Van Hollen Joins Markey, Merkley, Wyden in Urging Trump to Keep Longstanding Ban on South Korean Nuclear Enrichment, Reprocessing

Today, U.S. Senators Chris Van Hollen (D-Md.) joined Ron Wyden (D-Ore.) and co-chairs of the Nuclear Weapons and Arms Control Working Group, Senators Edward J. Markey (D-Mass.) and Jeff Merkley (D-Ore.), in writing to President Trump to urge the strongest possible non-proliferation measures in any revised nuclear cooperation agreement with South Korea. The Senators' letter follows the White House's release of a fact sheet on November 13 outlining the Trump administration's plans to allow uranium enrichment and spent fuel reprocessing for peaceful uses in South Korea. The Trump administration's action reverses long-standing bipartisan U.S. policy to prevent the spread of enrichment and reprocessing technologies to limit the risk that those capabilities could be used to produce fissile materials for weapons.

In the letter, the senators wrote, "South Korea's complicated history with nuclear weapons, and your role in that history, makes your policy shift particularly concerning. South Korea has had an interest in nuclear weapons stretching back to the 1970s and conducted illicit activities that were investigated by the United Nations. In 2016, you suggested that South Korea should develop nuclear weapons. In 2024, the Biden administration designated South Korea a 'sensitive country,' a term used for states that pose a proliferation risk. At the time, the former South Korean President Yoon Suk Yeol was being impeached for declaring martial law. Yoon had suggested that South Korea may need to pursue nuclear weapons to deter North Korea."

The lawmakers continued, "Providing latent nuclear capability to South Korea would also undermine U.S. non-proliferation efforts. For example, the United States is currently negotiating a 123 agreement with Saudi Arabia, which has also expressed nuclear weapons aspirations and is also seeking to enrich uranium. As some of us wrote to your State Department on November 17, 2025, the Administration should apply the strongest 'gold standard' protections to prohibit enrichment and reprocessing in all nuclear cooperation agreements. Agreeing to weaker nonproliferation measures with South Korea would make it harder to hold the line on Saudi Arabia, undermining the existing global nonproliferation regime and exacerbating tensions across the Middle East."

The senators request answers to the following questions by February 13, 2026:

1. Does the Administration intend to revise its 123 agreement with South Korea? If so, what revisions will be made? Is the Administration seeking "gold standard protections"?
2. Will the Administration inform the Senate Foreign Relations and the House Foreign Affairs committees about its intentions with respect to a revised 123 agreement with South Korea?
3. What nuclear technology is the Administration planning to provide to South Korea, who will provide it, when will it be transferred, and under what terms?
4. Is the United States considering constructing and operating enrichment and reprocessing facilities on South Korean soil?
5. Who will build the nuclear-powered attack submarines, where will they be built, what type of fuel will they use, and where will that fuel be produced?

Text of the letter can be viewed here and below:

Dear President Trump:

Last year, in a major reversal in policy, you pledged U.S. support for South Korea to enrich uranium and separate plutonium, the key ingredients for nuclear weapons. Seoul, an important U.S. ally, says this shift is necessary to advance its civil nuclear program and that it has no interest in nuclear weapons. Nevertheless, South Korean leaders have long been interested in keeping the nuclear option open, a possibility that you have encouraged. We are greatly concerned that giving Seoul the tools to make nuclear weapons will increase the risks of proliferation and a dangerous arms race, both in the region and beyond. Instead, we urge the Administration to apply the strongest possible "gold standard" non-proliferation measures in any revised nuclear cooperation agreement with South Korea.

South Korea has long sought approval from the United States to develop enrichment and reprocessing capabilities for civil purposes. The United States has repeatedly denied Seoul's requests-until now. According to a November 13 White House factsheet, during your October 29 meeting with South Korea, the United States said it "supports the process that will lead to [South Korea's] civil uranium enrichment and spent fuel reprocessing for peaceful uses." This reverses Washington's long-standing bipartisan policy to prevent the spread of enrichment and reprocessing technologies to limit the risk that those capabilities could be used to produce fissile materials for weapons.

The November 13 factsheet says that any enrichment and reprocessing must be consistent with the existing "123 agreement" between the two countries. Named after section 123 of the U.S. Atomic Energy Act, the bilateral agreement requires Seoul to obtain U.S. consent before enriching or reprocessing nuclear materials transferred under the deal or produced by technology transferred under the deal.

Seoul originally agreed to forgo enrichment and reprocessing when it first signed a nuclear cooperation agreement with Washington in 1972, but it pushed to revisit the issue when the agreement was renewed in 2015. The 2015 agreement did not give consent for enrichment and reprocessing, but it did create a high-level bilateral commission to explore options for doing so.

South Korea's complicated history with nuclear weapons, and your role in that history, makes your policy shift particularly concerning. South Korea has had an interest in nuclear weapons stretching back to the 1970s and conducted illicit activities that were investigated by the United Nations. In 2016, you suggested that South Korea should develop nuclear weapons. In 2024, the Biden administration designated South Korea a "sensitive country," a term used for states that pose a proliferation risk. At the time, the former South Korean President Yoon Suk Yeol was being impeached for declaring martial law. Yoon had suggested that South Korea may need to pursue nuclear weapons to deter North Korea.

The current South Korean president, Lee Jae-Myung, is not calling for nuclear weapons development, but there is still an active debate in South Korea regarding the security value of nuclear weapons. Surveys have found as many as 70 percent of all South Koreans supporting an independent nuclear arsenal, fueled in part by doubts about whether the United States is still committed to Seoul's defense. South Korea also has ballistic missiles powerful enough to deliver nuclear warheads and has an advanced nuclear industry that it could leverage if it decides to go nuclear. Allowing South Korea to develop a "latent" nuclear weapons capability would be highly destabilizing on the Peninsula. North Korea responded to the announcement by accusing the United States of giving South Korea the "green light" to become a "quasi-nuclear weapons state."

Providing latent nuclear capability to South Korea would also undermine U.S. nonproliferation efforts. For example, the United States is currently negotiating a 123 agreement with Saudi Arabia, which has also expressed nuclear weapons aspirations and is also seeking to enrich uranium. As some of us wrote to your State Department on November 17, 2025, the Administration should apply the strongest "gold standard" protections to prohibit enrichment and reprocessing in all nuclear cooperation agreements. Agreeing to weaker nonproliferation measures with South Korea would make it harder to hold the line on Saudi Arabia, undermining the existing global nonproliferation regime and exacerbating tensions across the Middle East.

You have also announced support for South Korea's plan to build nuclear-powered attack submarines. The November 13 factsheet did not contain details on the location of construction or where the nuclear fuel would come from. The bilateral nuclear agreement prohibits South Korea from using any U.S. origin nuclear material "for any military purposes," including submarine propulsion.

In light of our concerns, we request that you answer the questions below in writing by February 13, 2026:

1. Does the Administration intend to revise its 123 agreement with South Korea? If so, what revisions will be made? Is the Administration seeking "gold standard protections"? If not, why not?

2. Will the Administration inform the Senate Foreign Relations and the House Foreign Affairs committees about its intentions with respect to a revised 123 agreement with South Korea? If so, when? If not, why not?

3. What nuclear technology is the Administration planning to provide to South Korea, who will provide it, when will it be transferred, and under what terms? Who will pay for the technology and how much will it cost?

4. Is the United States considering constructing and operating enrichment and reprocessing facilities on South Korean soil? If so, under what terms?

5. Who will build the nuclear-powered attack submarines, where will they be built, what type of fuel will they use, and where will that fuel be produced? We urge the Administration to include the strongest possible non-proliferation measures in any revised nuclear cooperation agreement with South Korea. The security of the United States and our allies depends on it. Thank you in advance for your attention to this important matter.

Sincerely,