US President Donald Trump says North Korea "will be met with fire and fury like the world has never seen" if it threatened the United States again.
"North Korea best not make any more threats to the United States. They will be met with fire and fury like the world has never seen," Trump told reporters at the Trump National Golf Club in Bedminster, New Jersey.
It comes as North Korea said on Wednesday that it was considering strikes near US strategic military installations in Guam with its intermediate range ballistic missiles, according to South Korea's Yonhap news agency.
Trump's 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 US 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.
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.
Australian Strategic Policy Institute senior defence analyst Dr Malcolm Davis told SBS World News that despite the US and allies' attempts to reach a peaceful solution with North Korea, there was a 'pretty good' chance Kim Jong-un could launch a nuclear strike as early as next year.
"We have been rushed towards a precipice with a war in the next 12 to 18 months in the Korean peninsula," he said.
"We are 12 months away from a serious military crisis where US will need to stop the threat."
His comments came after a meeting between foreign ministers of ASEAN in Manila on Monday when North Korea Foreign Minister Ri Yong-ho asserted his country's nuclear program was justified, describing it as "a legitimate option for self-defence in the face of clear and real nuclear threat posed by the US against the DPRK."
North Korea can fit nuke in missile: reports
An annual defence white paper from Japan and a Washington Post report both assert that North Korea may have produced a miniaturised nuclear warhead.
North Korea may have successfully produced a miniaturised nuclear warhead that can fit inside its missiles, passing a key threshold in becoming a full-fledged nuclear power, according to a Japanese defence paper and a US media report.
The UN Security Council this weekend slapped its toughest sanctions yet on North Korea over its latest test of a ballistic missile that could be used to deliver a nuclear weapon. Despite the rapid tempo of these tests, uncertainty has lingered over the isolated nation's ability to couple such a missile with a nuclear device.
Those uncertainties appear to be receding.
Japan's Defence Ministry concluded in an annual white paper released Tuesday that "it is possible that North Korea has achieved the miniaturisation of nuclear weapons and has developed nuclear warheads." Japan, a key US ally, is also a potential target of North Korean aggression.
And The Washington Post reported Tuesday that US intelligence officials assess that a decade after North Korea's first nuclear test explosion, Pyongyang has produced nuclear weapons for ballistic missile delivery, including by intercontinental missiles - the type capable of reaching the continental US.
The Post story, citing unnamed US intelligence officials, said the confidential analysis was completed last month by the US Defence Intelligence Agency. The US also calculated last month that North Korea has up to 60 nuclear weapons, the Post said, more than double most assessments by independent experts.
Officials at the agency would not comment Tuesday on the report. The Office of the Director of National Intelligence could not immediately be reached for comment.
Alarm in Washington over North Korean leader Kim Jong Un's pursuit of a nuclear capability has intensified in the past month after the North conducted two tests of intercontinental ballistic missiles for the first time last month.
Technical hurdles
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.
"North Korea likely made some of the key measurements required to define those extreme conditions during the two July tests, but I can't imagine it has learned enough to confidently make a warhead that is small and light enough and sufficiently robust to survive," Stanford University expert Siegfried Hecker said in an interview with the Bulletin of the Atomic Scientists.
The former Los Alamos National Laboratory director said he did not think North Korea yet has sufficient missile or nuclear test experience "to field a nuclear warhead that is sufficiently small, light and robust to survive an ICBM delivery."
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 as well as Pyongyang's history of abducting Japanese citizens to train its spies.
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.
