U.S. Secretary of State Condoleezza Rice is in South Korea for talks expected to focus on North Korea's nuclear program.
Ms. Rice is due to meet on Sunday in Seoul with President Roh Moo-hyun and other South Korean officials.
On Saturday, Secretary Rice toured a military command bunker south of Seoul.
Ms. Rice told U.S. and South Korean troops at the bunker they face a daily threat from a country that -- in her words -- "is not free and does not have the best interests of its people at heart."
Ms. Rice, who is on an Asian tour, made her remarks as U.S. and South Korean forces began a week of joint military exercises.