The issue focused largely on the impact of the U.S. and China's military build-up on the region's stability and security.

But in the face of increasing Chinese military power and its aggressive rhetoric, the U.S., South Korea and Japan will have to make tough choices on the Korean Peninsula, U.S. Army Gen. Mark Milley, chief of staff of the Combined Forces Command, warned.

"We are not there yet, but we are getting closer every day,"