John Kirby said the US is also always looking for ways to get better information about the North. US Indo-Pacific Command was ordered to intensify its intelligence, surveillance and reconnaissance (ISR) collection activities in waters near the Korean Peninsula in early March following a series of North Korean missile tests.

South Korea and the US plan to kick off regular combined air force drills next week, informed sources said Tuesday, in yet another move to highlight their defense posture especially against North Korea's evolving missile threats.

The allies are set to begin the two-week Korea Flying Training next Monday, the eve of the inauguration of President-elect Yoon Suk-yeol, who has vowed to bolster the Seoul-Washington security alliance under his slogan of "peace through strength."