South Korea-US alliance explained: How China and Taiwan are reshaping the relationship

Beyond military issues, Trump has linked defence to trade and spending

South Korea’s new president, Lee Jae Myung, is making his first official visit to Washington to meet President Trump. The two leaders share dramatic political histories, but their approaches to the alliance diverge. Lee must balance his promise of loyalty to the US with concerns that Trump’s priorities — especially around China and Taiwan — could expose South Korea to new risks while weakening its defence against North Korea, the New York Times reported.

Strategic flexibility debate

The Trump administration is pushing Seoul to allow US forces stationed in South Korea to be deployed more freely in a potential conflict with China. This “strategic flexibility” raises fears in Seoul that US troops could be pulled into a Taiwan war, leaving South Korea vulnerable to North Korean aggression. Officials stress that flexibility should not undermine deterrence on the peninsula, but Trump’s unpredictability has fuelled anxiety.

Historical promises and new pressures

South Korea has long resisted involvement in regional conflicts outside the Korean Peninsula. A 2006 joint statement established that Seoul would not be forced into unwanted regional wars. But with Washington increasingly focused on China, analysts now question whether the US might reduce its military presence in South Korea if Seoul resists demands for greater flexibility. Some warn this could force South Korea into a painful recalibration of its defence strategy.

Security, trade, and money

Beyond military issues, Trump has linked defence to trade and spending. Last month, Washington agreed to cut tariffs on South Korean exports in exchange for a $350 billion investment package. Trump also wants Seoul to pay $10 billion annually for US troop upkeep — nine times more than current levels. These steep demands have fuelled domestic debates, with growing support among South Koreans for building independent nuclear weapons as a safeguard.

Regional coordination

On his way to Washington, Lee stopped in Tokyo to meet Prime Minister Shigeru Ishiba. The two leaders agreed to improve ties with each other and coordinate with the US to counter China and North Korea. Their discussions also touched on Trump’s tariffs and his calls for allies to shoulder more military spending. By presenting a united front with Japan, Lee hopes to strengthen his hand in talks with Washington.

Looking ahead

Trump insists US troops in Korea should be stronger against the North so they can “do other things” elsewhere. For Seoul, the challenge is ensuring that US strategic flexibility does not come at the expense of its own security. As Trump leans on allies to align with his China strategy, South Korea faces a pivotal decision: how much it can concede without losing its independence in shaping its defence posture.