War of words between the US and North Korea continues a day after Pyongyang said if would retaliate with nuclear weapons against any preemptive measures by Washington.
President Donald Trump issued an apocalyptic warning to North Korea on Tuesday, saying it faces "fire and fury" over its missile program, hours after US media reported Pyongyang has successfully miniaturised a nuclear warhead.
"North Korea best not make any more threats to the United States," said Trump, who was speaking from his golf club in New Jersey. "They will be met with fire and fury like the world has never seen."
Trump's warning came shortly after The Washington Post quoted parts of a Defense Intelligence Agency analysis as saying officials now think North Korea has "nuclear weapons for ballistic missile delivery" – including in its intercontinental ballistic missiles.
The Pentagon did not comment on the report, but the Post said the assessment's broad conclusions were verified by two US officials familiar with the analysis, and CNN said it had confirmed the report.
TRT World's Jon Brain brings latest from Washington DC.
Trump said North Korean leader Kim Jong-Un "has been very threatening beyond a normal state."
"As I said, they will be met with the fire and fury and, frankly, power," he told reporters.
The remarks mark a quick rise in rhetoric from the United States. Previous administration comments have focused on finding non-military solutions.
Pentagon spokesman Lieutenant Colonel Chris Logan said the United States seeks a peaceful de-nuclearisation of the Korean Peninsula, but he warned military action is never off the table.
"We remain prepared to defend ourselves and our allies and to use the full range of capabilities at our disposal against the growing threat from North Korea," Logan said.
The Post said it was not known if North Korea had successfully tested the smaller warhead design, although North Korea last year claimed to have done so.
The reported progress suggests North Korea is further along the path to having a deployable nuclear missile than had previously been acknowledged.
Experts had until last month said it would still take another two or three years for North Korea to develop a nuclear-tipped ICBM. But that calculus suddenly changed after Pyongyang last month tested two ICBMs – the first time Kim had demonstrated such a capability.
The first of these trials showed the rocket had the potential range to hit Alaska.
The second rocket tested last week flew even longer, with some experts even suggesting that New York could be vulnerable.
The Post also reported that another intelligence assessment estimated that North Korea now has up to 60 nuclear weapons, more than previously thought.
Despite the advance, North Korea still must overcome technical hurdles before it can claim to have perfected its nuclear weapons technology.
After Kim's second ICBM test, experts said it appeared the "re-entry vehicle" that would carry a warhead back into Earth's atmosphere from space had failed.
Without proper protection during a re-entry stage, a missile's warhead could burn up.
News that Kim appears to have produced a small nuclear warhead comes as international tensions around Pyongyang's program ratchet up ever higher.
"Especially since last year, when it pushed ahead with two nuclear tests and launched more than 20 ballistic missiles, it has posed a new level of threat," Japan's defense ministry said in an annual report that also reiterated concerns over China's increasing military posture.
Japan, which lies across the sea from North Korea, has been wary for decades over its missile development.
The most recent ICBM test saw the failed re-entry vehicle splash down into waters off Japan's Hokkaido island.
North Korea has vowed that tough new UN sanctions agreed over the weekend would not stop it from developing its nuclear arsenal, rejecting talks and angrily threatening retaliation against the United States.