South Korea is the world’s fourth-largest steel exporter and in 2017 the U.S. was its third-largest export market by volume. It is also a major U.S. ally in Asia, and South Korea relies on American military might as a shield from its belligerent, nuclear-armed neighbor to the north.

“We have a very big trade deficit with [South Korea], and we protect them,” Trump reportedly told donors. “We lose money on trade, and we lose money on the military. We have right now 32,000 soldiers on the border between North and South Korea. Let’s see what happens.”