An armed conflict on the Korean Peninsula can no longer be contained only to the area as North Korea's long-range missile capabilities could threaten the continental US, the top US military official said.

Marine Corps Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, made the remark in a message to the latest edition of the Joint Forces Quarterly, a National Defense University magazine, stressing that military decision-making needs to exceed the speed of events.

"There was a time, not long ago, when we planned for a conflict that might be contained to the peninsula. But today, North Korea's intercontinental ballistic missile, cyber, and space capabilities could quickly threaten the homeland and our allies in the Asia-Pacific region," Dunford said.

"Deterring and, if necessary, defeating a threat from North Korea requires the Joint Force to be capable of nearly instant integration across regions, domains, and functions," he said. 

"This means more than just fielding cutting-edge technologies that ensure a competitive advantage across all domains something we must continue to do. Keeping pace with the speed of war means changing the way we approach challenges, build strategy, make decisions, and develop leaders," he added.

Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford (left) shakes hands with US Secretary of Defense James Mattis as Mattis (Yonhap)