"The Hwasong-15 is also large and powerful enough to carry simple decoys or other countermeasures designed to challenge America's existing national missile defense system."

The new missile also features a more efficient and simpler steering mechanism, among other technological improvements, and appears to be able to deliver a 1,000-kilogram payload to anywhere in the US, according to Elleman.

But North Korea has "almost certainly" developed a nuclear warhead that weighs less than 700 kg, he added.

"The appearance of the Hwasong-15 marks a significant improvement in North Korea's ability to target the US How many more tests North Korea will undertake depends on the regime's perceived needs?" Elleman wrote.

North Korea will need to test the missile on a standard trajectory, not a lofted one, at least once or twice to validate its performance, and even more times to guarantee its reliability and accuracy.

"However, if low confidence in the missile's reliability is acceptable, two or three test firings over the next four to six months may be all that is required before Kim Jong-un declares the Hwasong-15 combat ready," he added, referring to the North Korean leader. (Yonhap)