Although missile may be tested it is likely to fail with a successful model possibly two to three years away

North Korea is capable of fulfilling its New Year’s threat to start testing an intercontinental ballistic missile in 2017, bringing a long-brewing standoff with the US to the boil in the first year of a Trump administration, weapons experts have warned.

Those experts said the regime in Pyongyang was likely to encounter multiple test failures in developing a two- or three-stage missile capable of reaching the continental United States or Europe, and that it would probably take a few years for such a weapon to become operational. But the first test would trigger a foreign policy crisis in Washington and western capitals.

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The looming crisis has sharpened into a battle of personal wills even before Donald Trump takes office on 20 January. On New Year’s Day, the North Korean dictator, Kim Jong-un, declared the country had “entered the final stage of preparation for the test launch of intercontinental ballistic missile [ICBM]”.

He further warned that his country would continue to build up its “capability for preemptive strike” as long as the US and its regional allies kept up their own nuclear threat and “stop their war games they stage at our doorstep”.

In response, Trump fired off a tweet, suggesting Kim’s regime would not reach that goal. “North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the US. It won’t happen!” the president elect declared on Twitter.

The tweet left it unclear whether Trump meant that North Korea lacked the capacity to build an ICBM or whether his administration would stop it. If the latter, it was also unclear how that would be done. North Korea’s fast growing nuclear weapons programme is a problem that has defied easy solutions.

Any attempt at a pre-emptive military strike would very likely trigger a ferocious response, quite possibly with short- and medium-range nuclear weapons aimed at South Korea and US bases in the region.

However, the Obama administration’s “strategic patience” approach, based on the hope that concerted international economic pressure would ultimately force North Korea to curb its nuclear activities, failed dramatically to reach its objective.

Over the eight years of the Obama administration, multilateral talks stalled and North Korea rapidly accelerated its programme, carrying out four nuclear tests and more than 50 missile and rocket launches.

Kim revelled in his regime’s technical successes in his New Year’s address

“We conducted the first H-bomb test, test-firing of various means of strike and nuclear warhead test successfully to cope with the imperialists’ nuclear war threats, which were growing more wicked day by day,” the North Korean leader said.

There are different opinions on whether North Korea succeeded in testing a hydrogen bomb exactly a year ago. Air sampling after the underground blast was inconclusive. US officials were quoted as saying it may have been a test of components of such a powerful thermonuclear warhead, rather than a fully-assembled weapon.

But there has been no doubt about the array of land and sea-based missiles of different ranges the North Koreans have tested, including satellite launch rockets, leaving an ICBM as the last major goal outstanding.

There is uncertainty over Pyongyang’s capacity to make a nuclear warhead small enough to put on missile. Following Kim Jong-un’s address on Sunday, the state department spokesman, John Kirby, said: “We do not believe that at this point in time he has the capability to tip one of these [missiles] with a nuclear warhead ... but we do know that he continues to want to have those capabilities and the programs continue to march in that direction.”

It is unclear whether Kirby was referring to all missiles or just ICBM’s. In the past, US military and intelligence officials have said they do believe the North Koreans can make a warhead that can be fitted on the No-dong missile, an established and well-tested weapon based on the Scud missile, with a range of up to 1600 km.

A nuclear-tipped ICBM would require a further technical leap, with a much longer range and a re-entry vehicle capable of withstanding the heat and vibration of plummeting through the earth’s atmosphere. However, there are ample signs North Korea is preparing to make that leap.

Melissa Hanham, a nonproliferation expert at the Middlebury Institute of International Studies in California, said the North Korean regime has been offering glimpses in 2016 of its planned ICBM, the KN-08 and testing components: the first and second stage, and a possible heat shield for a reentry vehicle.

The KN-08 - and its planned three-stage variant, the KN-14 - are designed to be truck-mounted so they can be moved around and hidden in caves until they are wheeled out, fuelled and fired.

Hanham said that pictures of missile engine tests also suggested the North Koreans had changed the liquid fuel they are experimenting with to UDMH/NTO a Soviet-pioneered propellant used in several space launch programmes.

“That’s a more energetic fuel, that allows you to jump to a higher rung in terms of how far you can go and how much weight you can carry,” Hanham said. A multi-stage missile with such fuel could not just reach the west coast, she added, but “it could even hit the eastern US”.

“They would have to do some flight testing, but there is no reason they can’t start that in 2017,” Hanham said.

A recent North Korean defector, Thae Yong-ho, a former deputy ambassador to London, said last week that the Pyongyang regime viewed 2017 as an opportunity to race ahead with its nuclear ambitions as a new administration finds its feet in Washington and South Korea is hamstrung by the impeachment of its president, Park Geun-hye. He said the goal was developing operational nuclear weapons “at all costs by the end of 2017”.

Perfecting a weapon capable of reaching the US and Europe would take longer, Michael Elleman, a missile expert at the International Institute for Strategic Studies, said.

“As for a possible ICBM test flight, I judge that North Korea could conduct one this year, but it is likely to fail,” Elleman said. He pointed out that tests of North Korea’s intermediate-range missile, the Musudan, have produced only one success this year among multiple failures, and argued Musudan engines would be likely to power the first stage of an ICBM.

“It would be foolish, from an engineering perspective, to rush prematurely a flight test of the more complex ICBM,” he said.