How Seoul’s Break With Kyiv Serves Trump’s Russia Turn

On Oct. 9, President Donald Trump announced that Russia would supply nearly five million tons of diesel to American and global markets, and the Treasury licensed the trade shortly afterward. The next day he said it was time for Ukraine to get a new president, and demanded that Kyiv stop striking Russian refineries while making no matching demand of Moscow over Ukraine's power grid. On Oct. 16, two days before its tariffs on buyers of Russian energy were due to take effect, he waived the main provisions of the Graham Sanctioning Russia and Iran Act, a law he had signed on Sept. 18.

Seoul, meanwhile, has recalled its ambassador to Ukraine and is withdrawing about half of its embassy staff in Kyiv, although it says its aid to Ukraine will continue. The quarrel began on Sept. 23, when Zelensky told the UN General Assembly that Ukraine had handed two captured North Korean soldiers to Seoul. South Korea says both sides had agreed to keep the transfer secret, and Ukraine denies that any such agreement existed. Seoul did not mean any of this as a favor to Washington. The effect does not depend on intent, because an Asian democracy publicly breaking with Kyiv lowers what Trump pays at home for turning toward Moscow.

Washington set its course on Russia for its own reasons, with diesel above $6 a gallon a month before the midterms and a president who blames Ukrainian refinery strikes for the price. Bipartisan critics called the waiver a gift to Putin, and their case rests on allied solidarity with Ukraine, because pressuring Kyiv is hard to defend while other democracies stand behind it. European diplomats in Seoul have already begun to say, as the Financial Times reported on Oct. 28, that South Korea is not really like-minded. A Western-aligned Asian democracy publicly accusing Zelensky of breaking his word makes Trump's complaints about him look less isolated, and each such defection, even by a second-tier ally, makes the next concession cheaper.

The waiver also widens Seoul's options, since before Oct. 16 a country that knowingly bought Russian oil risked U.S. tariffs of up to 100% on its exports to the United States. With Russian diesel now trading under a Treasury license that runs to April 2027, the remaining barriers to Korean purchases of Russian crude are Seoul's sanctions policy and its standing with Europe and Ukraine's other backers. The quarrel with Kyiv has already worn down the second of those two barriers.

The cost to Seoul falls on intelligence, where Washington has withheld part of its satellite reporting on North Korea's nuclear and technology programs since early April, after Unification Minister Chung Dong-young publicly named a suspected enrichment site at Kusong. On Oct. 8, the chairman of the Joint Chiefs of Staff told the National Assembly that sharing had still not fully returned to normal. The quarrel with Kyiv now endangers a second source, since the National Intelligence Service itself assesses that North Korea's army gained modern combat tactics and battlefield data in Russia at a cost of about 6,000 casualties. Ukraine fought those units and is the outside party best placed to know what they learned. That same service pledged in January 2025 to work with Ukraine's intelligence services on North Korea's role in the war, and that cooperation depends on goodwill the quarrel is eroding.

Seoul bears the cost of this quarrel while Washington collects the benefit, since Kyiv now faces pressure from two allied capitals instead of one and Washington never had to ask Seoul for its share. Kyiv and its European backers should keep that pattern from spreading to Washington's other Asian partners. Ukraine has the means through Brussels since the EU signed security and defense partnerships with both Japan and South Korea in 2024 and Seoul's diplomats and arms makers need goodwill in Europe. Closing the dispute with Seoul quickly, on terms Lee can present at home as the apology he demanded, would remove the precedent before anyone else in the region is tempted to follow it.

Sang Won Pyo is a research assistant to Dr. Bader Al-Saif, associate fellow at Chatham House. His work has appeared in Cambridge Manara Magazine, the Middle East Institute at the National University of Singapore, and the S. Rajaratnam School of International Studies. He previously served as a legislative assistant in the office of the chairperson of the National Policy Committee and in the offices of members of the Foreign Affairs and Unification Committee of the National Assembly of the Republic of Korea.