North Korea tests 'threaten international peace'
Mr Obama will be giving his annual state of the union address later this evening. Several diplomats said it was possible that was why North Korea chose this day to detonate an atomic device, since Pyongyang traditionally makes such moves on important days in the US calendar.
China's reaction was more muted. In Beijing, Chinese Foreign Minister Yang Jiechi summoned the North Korean ambassador to China to protest against the North's new nuclear test. Mr Yang said China was "strongly dissatisfied and resolutely opposed" to the test.
Several council diplomats said the United States and its allies would push for tough new sanctions rather than merely expanding existing measures imposed after Pyongyang's 2006 and 2009 atomic tests.
US ‘not threatened’
North Korea's third nuclear test may be aimed at showing its foes it can develop a warhead for a missile but it is still a long way from being able to threaten the United States, proliferation experts say.
The secretive Asian state is widely believed to be trying to develop a device that is compact and light enough to fit on top of a missile. North Korea said the test, which was condemned by world powers, had used a miniaturised device.
Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) executive secretary Tibor Toth said the action "constitutes a clear threat to international peace and security and challenges efforts to strengthen global nuclear disarmament and non-proliferation".
The international monitoring agency said the "explosion-like" event that North Korea described as a nuclear test had a seismic magnitude of 5, around twice as large as a test it carried out in 2009 and much bigger than one in 2006.
"It seems as if Pyongyang wants to send the message - true or not - that it can employ a missile with a nuclear warhead and that previous problems with their nuclear tests have been overcome," Jim Walsh of Massachusetts Institute of Technology (MIT) said.
No lies on test
The North's ultimate aim, Washington believes, is to design a ballistic missile capable of carrying a nuclear warhead that could hit the United States. Pyongyang says the programme is aimed merely at putting satellites in space.
However, North Korea still had a long way to go before it could credibly threaten the United States with nuclear weapons, said Daryl Kimball from the Arms Control Association, a US-based research and advocacy group.
"It is likely to be years away from fielding an ICBM which could deliver a nuclear warhead to the US mainland," he said.
Kimball said the test was an embarrassment for China's leadership and Pyongyang may have jeopardised the aid and diplomatic support it receives from Beijing.
China criticised the previous tests but did not roll back on aid. But Beijing had signalled that if North Korea undertook further tests, it would not hesitate to reduce assistance.
Test ‘threatens stability’
Tánaiste Eamon Gilmore condemned “in the strongest possible terms, the test by North Korea of a nuclear explosive device”.
He said the test threatens peace and stability on the Korean peninsula and was a challenge to Irish foreign policy of advancing global nuclear disarmament.
“Nuclear weapons are never a means to guarantee peace and security; far from it, they pose the greatest threat of all. The regime in Pyongyang must realise that today’s act is reckless and provocative and will only isolate it further from the international community,” Mr Gilmore said.
He called for the Comprehensive Nuclear Test Ban Treaty to be immediately brought into force.