U.S. and South Korean troops have begun annual drills that come after tensions rose over North Korea's two intercontinental ballistic missile tests last month.
The Ulchi Freedom Guardian drills that began Monday are largely computer-simulated war games and will run through Aug. 31. Pyongyang calls the 11-day drills a "reckless" invasion rehearsal that could trigger the "uncontrollable phase of a nuclear war."
South Korea's President Moon Jae-in said Monday the drills are defensive in nature. He says the drills are held regularly because of repeated provocations by North Korea.
Earlier this month, Trump pledged to answer North Korean aggression with "fire and fury." North Korea, for its part, threatened to launch missiles toward the American territory of Guam.