Explainer-South Korea's nuclear dilemma: Would U.S. trade Seattle for Seoul?

South Korean President Yoon Suk Yeol delivers remarks to the U.S.-Korea Business Council at the U.S. Chamber of Commerce in Washington, D.C., U.S., April 25, 2023. REUTERS/Sarah Silbiger

At a summit with South Korean leader Yoon Suk Yeol on Wednesday, U.S. President Joe Biden will seek to reassure South Koreans that the U.S. nuclear umbrella is sufficient protection from North Korean attack.

But with North Korean missiles now a direct threat to the United States, an old Cold-War dilemma has resurfaced: would the United States risk nuclear retaliation against itself to defend an ally?