U.S.-South Korea Relations at the Outset of a New Era: Challenges and Opportunities for Regional Alignment and New Frontiers
SUMMARY
In the fall of 2025, it was clear that the world had entered a new era after a thirty-five-year post–Cold War interregnum. U.S. President Donald Trump’s disruption of global trade and Chinese President Xi Jinping’s assertion of Sinocentrism compounded the military impact of Russian President Vladimir Putin’s war in Ukraine and North Korean leader Kim Jong Un’s demand that the international community treat North Korea as a nuclear power. In place of globalization, regions faced new security dilemmas as commercial ties became inseparable from economic security. In these circumstances, U.S.–South Korea relations were beginning to re-form along two axes: in security, facing questions of a new regional alignment; and at the intersection of economics and security, facing frontiers not previously explored, including tariffs, energy projects, and joint shipbuilding endeavors.
Even as 2025 offered plentiful opportunities for looking back, it proved to be a key turning point that gave new urgency to looking forward. The eightieth anniversary of the end of World War II showcased China–Russia–North Korea conviviality, unlike previous decade remembrances that had tested Japan’s relationship with South Korea and China. Serving also as the sixtieth anniversary of South Korea–Japan normalization, the year saw an unparalleled frequency of shuttle diplomacy, despite the arrival of new leaders testing mutual trust. Looking ahead, the articles in this volume of Korea Policy point to what is now changing.
The two most striking developments in 2025 were the tariffs imposed by Trump, which unsettled the international economic order that had largely been in place since the early postwar years, and the entrenchment of the Russia–North Korea alliance, which ended the near-total isolation of Pyongyang that had prevailed since the end of the Cold War. Our authors assess how the U.S.–South Korea alliance is responding to the new Russia–North Korea relationship and how it is coping with the overall state of security in the Indo-Pacific, especially given China’s more assertive posture. A second set of papers looks at the impact of U.S. tariffs on U.S.–South Korea relations, the prospects for improved South Korea–Japan ties, and the quest for trilateral U.S.–South Korea–Japan cooperation on natural gas development.
China’s maritime assertiveness is testing regional security, threatening not only Taiwan and the Philippines but also maritime boundaries with Japan and South Korea. As North Korea develops alliance relations with Russia and receives more recognition from China, its nuclear weapons programs grow more ominous. Coordination in response to intensifying dangers is proving challenging. Another complication is President Lee Jae Myung’s inclination toward maximum ambiguity at a time when Trump and Xi are pressuring states to take sides. Most of the authors call for tighter alliances in these circumstances to counter the Russia–North Korea alliance and expand the regional framework for the U.S.–South Korea alliance and trilateral cooperation.
The economic merits of alliance cooperation extend to new frontiers. Capturing the most attention is the challenge of deepening cooperation in the face of Trump’s unilateral tariff assault. Shipbuilding collaboration has risen to the forefront, meeting an urgent U.S. need if it can overcome severe hurdles. Also high on the Trump agenda is opening Alaska for vast liquefied natural gas exports, funded by Japan and South Korea and aligned with their future energy needs.
The Gyeongju Asia-Pacific Economic Cooperation summit provided an occasion to seal a trade deal between Seoul and Washington and stabilize the Indo-Pacific region after a tumultuous nine months. However, agreement details remained unclear, security challenges persisted, and South Korea stayed on the frontlines of a perilous environment.