North Korea has produced a miniaturised and missile-ready nuclear warhead, say US analysts

North Korea has vowed to send a 'pack of wolves' to defend itself

North Korea has stepped up its testing of missiles (Getty)

North Korea is said to be able to produce a miniaturised warhead that can fit inside the kind of missiles it has recently been testing and which analysts believe could reach the US mainland.

A US media report said that the finding was contained last month in an analysis completed by the US Defence Intelligence Agency. It said the intelligence community had recently concluded the East Asian nation had up to 60 nuclear weapons.

“The IC [intelligence community] assesses North Korea has produced nuclear weapons for ballistic missile delivery, to include delivery by ICBM-class missiles,” the assessment stated, according to the The Washington Post.

There has been no public, independent confirmation of the report and the news comes against a backdrop of mutual sabre-rattling by Washington and Pyongyang. As North Korea has continued to test intercontinental ballistic missiles (ICBMs) that potentially have the ability to reach Alaska or Hawaii, Donald Trump and his top officials have warned that “nothing is off the table” when it comes to dealing with the challenge.

A week ago, the US ambassador to the UN, Nikki Haley, said Washington would not seek UN Security Council action following North Korea’s latest missile test, because “the time for talk is over”.

Over the weekend, the UN Security Council unanimously voted to approve new sanctions that included a ban on coal and other exports worth more than $1bn. North Korea responded by saying it would launch a “thousands-fold” revenge against the US.

“We are ready to retaliate with far bigger actions to make the US pay a price for its crime against our country and people,” said the official Korean Central News Agency. It said it would send “packs of wolves” to “strangle” those nations opposing Kim Jong Un.

Secretary of State Rex Tillerson said on Monday North Korea could show it was ready for dialogue by stopping the missile tests.

“The best signal that North Korea could give us that they’re prepared to talk would be to stop these missile launches,” he said, speaking at the Association of Southeast Asian Nations (ASEAN) meeting in Manila.

Asked about a time frame within which the US wanted North Korea to halt its nuclear programme, he said: "We’re not going to give someone a specific number of days or weeks. This is not a ‘give me 30 days and we are ready to talk’. It’s not quite that simple. So it is all about how we see their attitude toward approaching a dialogue with us.”

USA Today said in a phone call on Sunday, Mr Trump and Moon Jae-in, his South Korean counterpart, “affirmed that North Korea poses a grave and growing direct threat to the United States, South Korea and Japan, as well as to most countries around the world”.

“The leaders committed to fully implement all relevant resolutions and to urge the international community to do so as well,” a White House statement said.

Mr Trump later tweeted: “Just completed call with President Moon of South Korea. Very happy and impressed with 15-0 United Nations vote on North Korea sanctions.”

The Post said that while it has been more than a decade since North Korea’s first nuclear detonation, many analysts believed it would be years before the country could design a compact warhead that could be delivered by missile to distant targets. It appears, that line has already been crossed.