SEOUL, South Korea (AP) — U.S. and South Korean officials vowed Wednesday to make North Korea pay a high price for its defiant nuclear test earlier this month that caused worries about advancement in the North's bomb program. After the bomb test, the rival Koreas resumed psychological warfare with Seoul blasting anti-Pyongyang broadcasts from border loudspeakers, while Pyongyang does the same and also floats propaganda leaflets over the border by balloon, according to South Korean officials.