Western scientists and intelligence agencies are racing to gather details of North Korea’s latest nuclear test, as diplomats, driven by the fear that Pyongyang is moving nearer to its goal of obtaining a nuclear-armed missile capable of hitting the US, scrambled to formulate their response.

In contrast to the largely symbolic tests of 2006 and 2009, the one conducted on Tuesday has raised real concerns that the North – which claimed to have detonated a “smaller and light” device using “diverse materials” – is on the way to an enriched uranium bomb. Such a device would be relatively easier to manufacture – although technically more advanced – than the plutonium technology North Korea has employed before.

Within hours of the test, South Korea raised its military alert level, while Japan sent aircraft to collect atmospheric samples to determine what type of device had been used. In Washington, newly installed Secretary of State John Kerry moved to reassure nervous allies of its support, while President Barack Obama warned in his State of the Union address that “provocations of the sort we saw last night” would only further isolate North Korea. The US, he declared, would strengthen its own missile defence and lead the world in “firm action” to counter the threat.

Download the new Independent Premium app Sharing the full story, not just the headlines

Scientists are expected to have a preliminary idea of the nature of the test within 24 hours. But even if the worst is confirmed, the familiar question arises: how can the West can respond, short of war, given that little scope remains for tightening already severe sanctions?

Britain took one of the few options available to it, summoning North Korea’s ambassador to the Foreign Office to “underline the UK’s firm opposition to this nuclear test and make clear to North Korea that it can either engage constructively with the international community, or face increasing isolation and further action...”.

The North “will want to send a message that high-level negotiations with the US are necessary,” said Cheong Seong-chang, an analyst at the private Sejong Institute in South Korea. He said that the two sides could hold talks later this year.

The key, as ever, lies with China, whose supplies of fuel and food keep the North afloat. This time, Beijing has expressed its clear displeasure at the test. But it shows no sign of stopping economic support.