The Koreas | Security | East Asia

South Korea, US Pull Apart as the Alliance Strains

Restricted intelligence sharing, an investment spat, and remarks by a U.S. commander point to a widening gap between the allies.

South Korean President Lee Jae-myung meets with U.S. President Donald Trump on the sidelines of the U.N. General Assembly in New York, Sep. 22, 2026.

South Korea and the United States are in a tug-of-war over the terms of their alliance. Since March the two governments have clashed over intelligence sharing, investment, and military command. The friction is now visible in small and concrete ways.

The dispute began on March 6 when the South’s Unification Minister Chung Dong-young named the North Korean city of Kusong as the site of a uranium enrichment facility. Washington treated the remark as a disclosure of classified information and has since partially restricted the imagery intelligence shared with Seoul on North Korea. Chung has said he learned of the facility from open sources. Washington did not accept the explanation. In April, National Security Adviser Wi Sung-lac acknowledged that the two governments held different views of the remark.

A second dispute has become entangled with the first. The U.S.-listed e-commerce company Coupang is under investigation in South Korea over a data breach. A July report by the U.S. House Judiciary Committee accused South Korea’s National Intelligence Service of pressuring officials to pursue the company; the NIS called the claim false. In the same April briefing, Wi said the Coupang case concerned a single company. He nonetheless acknowledged that it was affecting security talks and delaying negotiations.

The intelligence service has been affected directly. Washington barred the agency from a June meeting with Japan on North Korean cyber threats and notified Seoul in writing, according to local media reports. The agency called the exclusion a one-time measure. South Korean Ambassador to the U.S. Kang Kyung-hwa also confirmed that visas for two or three agency employees bound for the embassy in Washington had been delayed. The agency attributed the delays to stricter U.S. entry procedures and denied any link to the intelligence dispute. 

Each incident can be explained on its own, but together the impact is mounting on the intelligence relationship. 

Economic pressure has followed a similar course. Seoul hoped that progress on its $350 billion investment pledge under a trade deal with Washington would restart stalled security talks on nuclear-powered submarines and uranium enrichment. However, the specific terms of investment have become a cause of more tension.

U.S. President Donald Trump announced on September 30 that South Korea would invest $54 billion in the Alaska liquefied natural gas project. The trade ministry in Seoul said no decision had been made on whether to invest or how much. Trump pressed the point two days later. On October 2, he warned Seoul of higher costs for staying out of the project. He repeated the investment claim on October 14 in a post on Truth Social.

Before the November 3 midterm elections, Trump has been presenting investment pledges from allies as proof that his tariff policy works. Now Seoul is facing pressure to turn a campaign claim into a financial commitment. The link to security talks gives the dispute weight beyond money.

The strain is also jeopardizing a long-held South Korean military goal. The Lee administration aims to regain wartime operational control (OPCON) of South Korean forces by 2028. U.S. Forces Korea commander General Xavier Brunson – the officer who currently hold wartime OPCON over Korean forces – has cited the first quarter of 2029.

Then, on October 14, Brunson said at a policy forum in Washington that the conditions for the handover had changed. He pointed to recent North Korean missile launches as evidence. He voiced support for the OPCON transfer but opposed rushing it........

© The Diplomat