North Korea threat
North Korean leader Kim Jong Un claps during a demonstration of a new large-caliber multiple rocket launching system at an unknown location. KCNA via Reuters

More US analysts now believe it's likely North Korea has a miniature nuclear warhead that could fit on a missile — just as the nation has boasted. There's no official consensus yet in the US government on that assessment, but more observers who were originally skeptical are coming around to that view.

That's not to say North Korea is yet capable of successfully delivering the warhead to a target, reports CNN. If such a warhead exists it's evidence of the chilling speed with which Pyongyang has developed a nuclear-tipped ballistic missile — in defiance of UN sanctions — that could one day potentially strike the US.

A recent North Korean report said that the nation's hydrogen bomb was powerful enough to "immediately" kill everyone in Manhattan, and the city would "burn down to ashes." Recent photos show North Korean leader Kim Jong Un standing next to what Pyongyang officials claim is a miniaturized nuclear device. The photos are being scrutinised by American scientists for any indication of progress, officials said.

For the sake of prudent war planning, US commanders have said that they are assuming North Korea has a functional warhead — but have stopped short of declaring outright that it it exists. "It's the prudent decision on my part to assume that he has the capability to miniaturize a nuclear weapon and put it on an ICBM," Admiral William Gortney, head of US Northern Command, recently told Congress.

American officials also believe North Korea is making progress developing an advanced version of its KN-08 intercontinental ballistic missile. State media just released photos of Kim on site during an apparent test of a new solid-fuel rocket engine, a key component of the KN-08.

South Korea went on high alert after the test — and Kim's boast that the engine significantly advanced his nation's nuclear strike capabilities. There are indications that North Korea might be preparing for yet another underground nuclear test. Officials claimed in January that they had detonated a hydrogen bomb. But American authorities and others disputed the claim, based on a weaker seismic impact than a hydrogen bomb test would have created.