North Korea's alleged threat at last week's diplomatic talks in Beijing to test a nuclear weapon sent a chill through the region.
By Sarah Buckley
BBC News Online
Most analysts believe the threat was most likely to be a negotiating ploy, as the secretive state attempts to extract maximum concessions in return for ending its nuclear ambitions.
But given the unpredictable nature of Kim Jong-Il's regime, few are prepared to dismiss the threat out of hand.
N Korea's leaders seem to be sticking to a hard-line negotiating stance
"It just isn't in their interests right now," said Gary Samore, from the International Institute of Strategic Studies.
"It would make it easier for the US to mobilise international support to sanction North Korea," he told BBC News Online.
Even China and Russia, North Korea's closest allies in the region and those most opposed to sanctioning the impoverished state, would likely turn against Pyongyang if it went ahead with a test.
Investment in the region would be affected and Japan - China's main diplomatic competitor - might feel the need to bolster its defences, even to the extent of considering a nuclear arsenal itself.
"China is especially critical (to North Korea), given their role today as a fuel and food supplier," said James Clay Moltz, deputy director of the Center for Non-proliferation Studies at the Monterey Institute of Strategic Studies.
Peter Hayes at the Nautilus Institute in California said North Korea's test warning was "not a bluff, but also not necessarily a near-term threat. Rather, a way to kick Russia and China in the shins to get them to bring the US to the table with a credible roadmap of what they get if they trade in their nuclear deterrent."
Threatening a nuclear test gives North Korea diplomatic leverage.
But carrying one out would set off a chain reaction of crisis moves by the international community which could jeopardise Kim Jong-il's regime.
"I think (a nuclear test) would be a costly mistake. But that does not mean that they won't do it," said James Clay Moltz.
In-young Chun at Seoul National University agreed that such a warning could not be simply ignored.
"We cannot take lightly that kind of threat," he said.
A nuclear test would answer the long-debated question as to whether North Korea really has nuclear weapons and would give further ammunition to hawks in Washington who are pushing for regime change in Stalinist North Korea.
The practicalities of testing a nuclear weapon are not beyond North Korea, according to independent nuclear consultant John Large.
The standard depth that a nuclear test is conducted at is about 600 metres. But for a weapon of only 2-7 kilotons - thought to be within North Korea's capability - 50-60 metres' depth or cover is more than sufficient.
It would only take 1-2 weeks to excavate this and to set up the small test cavity in which the nuclear device would be placed and detonated, he said.
Such small-scale excavation would be difficult for American surveillance to detect.
But US monitors might be able to trace the chemicals used to make the initiator - the "front-end" of the nuclear weapon - which is used to generate an abundance of neutrons in the device for it to go super-critical, and create a powerful nuclear explosion.
John Large said it was unlikely that the North Koreans would use a very sophisticated initiator. It would probably be a simple device that used beryllium-polonium inserted into the fissile core or heart of the nuclear device.
The US is therefore likely to be looking for any signs of polonium production in North Korea's nuclear reactor at Yongbyon.
Because polonium degrades quickly, detecting the element would indicate that a test was scheduled for within two to three weeks.
If North Korea did carry out a test, the key question is whether the weapon was "the size of a fridge-freezer or a waste-paper bin", said John Large.
The latter would be far more worrying because it would be able to fit onto one of North Korea's proven missiles.
He said the difficulty hindering a firm analysis of North Korea's nuclear progress was its dependency on innovation.
"When a secretive regime such as North Korea has been embargoed and sanctioned for many years... there may occur the quite unintended encouragement for them to adopt ingenious and novel approaches to how they confront and solve problems.
"Such ingenuity may slip past the detection systems and rationale of a super technological state such as the United States," he said.