Defense Secretary Jim Mattis says the U.S. has not yet shot down any North Korean missiles because they have not posed a threat to the United States or its allies.
In remarks to reporters at the Pentagon, Mattis said Monday that if the missiles were perceived as a threat, "that would elicit a different response from us.''
Asked what that response is likely to be, Mattis refused to elaborate.
Earlier this month, North Korea tested what it described as a thermonuclear weapon suitable for mounting on an intercontinental ballistic missile.
At the beginning of this year, North Korean leader Kim Jong Un announced plans to develop a long-range intercontinental ballistic missile that can target the U.S. mainland.
On Monday, almost a dozen U.S., Japanese and South Korean warplanes armed with live weapons flew over the Korean Peninsula in what the U.S. military is describing as a "sequenced bilateral show of force" in response to North Korea's latest missile launch.
The Pentagon said the aircraft practiced their attack capabilities by releasing live weapons at a training range in South Korea. The two nations were joined by four Japanese F-2 fighter jets for additional formation training over waters near Kyushu, Japan.
In announcing the exercise, the U.S. Pacific Command said it "maintains the ability to respond to any threat in the Indo-Asia Pacific theater at a moment's notice." Aircraft involved in the exercise included two U.S. B-1B bombers, four U.S. Marine Corps F-35B Lightning advanced fighters and four South Korean F-15K fighters.
The exercise was conducted in response to North Korea's launch on Friday of an intermediate-range missile over Japan, its second such launch in under a month. The missile traveled 3,700 kilometers before landing in the northern Pacific Ocean and was the North's longest-ever test flight of a ballistic missile.