NORTH Korea has retaliated to Donald Trump's warning of "fire and fury like the world has never seen" by threatening a missile strike on US Pacific territory Guam.

The reclusive state announced it was "carefully examining" a plan to attack Guam, just hours after the US President issued his apocalyptic warning following reports North Korea had produced a missile-ready nuke.

In a statement released by North Korea's state-run KCNA news agency today, a spokesman for the Korean People's Army said the strike plan would be "put into practice in a multi-current and consecutive way any moment" once leader Kim Jong-un made a decision.

In another statement citing a different military spokesman, North Korea also said it could carry out a pre-emptive operation if the US showed signs of provocation.

US officials earlier said the Pyongyang regime has successfully produced a miniaturised nuclear warhead that can fit inside its missiles, according to reports.

If true, the development means the rogue state has crossed a key threshold on the path to becoming a fully-fledged nuclear power.

It also means it is potentially capable of packing the weapon of mass destruction inside an intercontinental ballistic missile.

The frightening claims were made in the Washington Post , citing a confidential assessment by the US Defense Intelligence Agency.

US President Trump told a press briefing on Tuesday that North Korea would be met with "fire and fury like the world has never seen" if they made any more threats to the United States.

Speaking at his golf club in Bedminster, New Jersey, Mr Trump said: "North Korea best not make any more threats to the United States."

He added: "He has been very threatening. As I said, they will be met with fire, fury and frankly power the likes of which this world has never seen before."

The latest revelations come a month after the US said that it believed that up to 60 nuclear weapons are now controlled by North Korean leader Kim Jong Un, far more than previously thought.

Intelligence analysts have been shocked by the fast development of North Korea's nuclear weapons program.

Many analysts believed it would be years before the country's weapons scientists could design a miniaturised nuclear warhead.

The revelation comes a day after North Korea said it would launch "thousands-fold" revenge against the US over the adoption of tough UN sanctions imposed after its intercontinental ballistic launches.

The North's statement came two days after the UN Security Council unanimously approved new sanctions to punish the North including a ban on coal and other exports worth over $US1 billion (A$1.26 billion).

Pyongyang's statement said the sanctions were caused by a "heinous US plot to isolate and stifle" North Korea.

Tension has been running high since the nuclear-armed North staged two successful ICBM tests last month, sparking global alarm over its rapidly-advancing weapons capabilities.

Also on Tuesday US president Donald Trump praised the international coalition coming together to pressure North Korea over its intercontinental ballistic missile launches "after many years of failure."​

"After many years of failure,​ ​countries are coming together to finally address the dangers posed by North Korea. We must be tough & decisive!​," the US leader wrote on Twitter.

News Corp Australia

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