The United Nations security council has threatened new punitive measures against North Korea after it claimed to have tested a hydrogen bomb, but it was far from clear that the international community would agree on a means to contain the regime’s nuclear weapons programme.

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The White House, echoing nuclear experts around the world, said its initial analysis was “inconsistent” with Pyongyang’s claims to have detonated a hydrogen bomb. Even a miniaturised device would be expected to have created a blast far bigger than the more rudimentary atomic bombs North Korea has tested previously, and the seismic data suggested the blast was no more powerful than the last test in 2013.

The shock wave did point towards a nuclear detonation of some sort, which would be the country’s fourth, in defiance of multiple security council resolutions and layers of international sanctions.

After Wednesday’s emergency meeting, the 15-nation council “strongly condemned” the apparent test – which triggered seismic shocks around the region – and described it as a “clear threat to international peace and security”. Ban Ki-moon, the UN secretary general, also said it was “profoundly destabilising for regional security”.

However, no concrete action was agreed at the security council meeting in New York, just a threat of unspecified measures to come.

Elbio Rosselli, Uruguay’s UN ambassador, who is acting as the council president this month, recalled the security council’s previously stated intention to take “further significant measures” if Pyongyang violated a string of UN resolutions by testing an atomic device.

“In line with this commitment and the gravity of this violation, the members of the security council will begin to work immediately on such measures in a new security council resolution,” said Rosselli. He did not give further details, but diplomats suggested that adding more regime members to the sanctions list was one of the options being considered.



Three previous North Korean nuclear tests in 2006, 2009 and 2013 triggered previous UN sanctions, and there are currently a total of 20 entities and 12 individuals on the UN sanctions blacklist.

Motohide Yoshikawa, Japan’s UN ambassador, warned that the council would damage its own credibility if new sanctions were not swift and “significant”.

In the past, North Korea has responded to UN sanctions with yet more defiant and combative acts, and few experts expect that new measures will bring Pyongyang to the negotiating table, particularly in the absence of consensus among the major powers on a negotiating strategy.



The US backs South Korea and its other regional allies in demanding that North Korea commit to dismantling its nuclear weapons programme before reconvening multinational negotiations, known as the six-party talks, which stalled in 2009.

Ash Carter, the US defence secretary, spoke by phone to his South Korean counterpart Han Min-koo, to restate US commitment to protect its ally, including “all aspects of extended deterrence” – a reference to a potential US nuclear response if Pyongyang attacked its southern neighbour with nuclear weapons.

China and Russia have argued that the six-party talks should recommence without preconditions. Barack Obama invested a great deal of political capital in concluding a multinational agreement with Iran last July, under which – in return for sanctions relief – Tehran accepted curbs on its civilian nuclear programme to limit the risk it could be diverted to making weapons. Now entering his last year in office, it is unclear whether Obama has the time or stamina to spearhead a new initiative on the North Korean programme.

China said it had been taken by surprise by the apparent test, and joined in the international protests. However, Beijing has been reluctant to apply too much economic pressure to its neighbour in the fear that it might trigger total fiscal collapse and create a potential flood of North Koreans across the border.

The seismic readings from the suspected test placed its origin at a site in the north-east of the country, Punggye-ri, which has been used in previous nuclear tests. It registered a magnitude of 5.1, similar to the 2013 test, which was estimated to have been caused by an atomic fission device with an explosive yield of between five and 10 kilotons. A hydrogen – or thermonuclear – bomb would be expected to produce a much greater blast even if miniaturised.

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The size of the blast led governments and experts to discount the possibility that the weapon test was a two-stage thermonuclear device of the sort developed by the established nuclear weapons powers. That combines a fission blast with a secondary fusion detonation. Experts say that a third option was a hybrid device in which a mostly fission device was boosted by fusion of small quantities of hydrogen isotopes.

Lassina Zerbo, the head of the preparatory commission trying to bring the 1996 comprehensive test ban treaty into force, said the best way for the international community to put pressure on North Korea or any other states contemplating nuclear tests, is for countries who have so far not ratified the treaty to join. Twenty years after the treaty was adopted by the UN, there are still eight key states who need to join for it to become legally binding. Five of those – the US, Iran, Israel, Egypt and China – have signed but not ratified it. Another three – North Korea, India and Pakistan – have not signed it.

“These eight countries should show leadership to ensure this doesn’t happen again,” Zerbo said. “We need people to work on this issue. We don’t want to see more tests before people think this treaty is important. The only way to stop this is to make it legally binding. I hope this will be the last wake-up call to the international community to act on this treaty.”