It's an about face for Pyongyang, which exploded its first nuclear device just three weeks ago.
The research climaxed in October 2006 when North Korea first tested a half-kiloton nuclear device.
Israeli intelligence believes Tehran will have a nuclear device by the end of 2009.
North Korea said it successfully detonated a miniaturized nuclear device at a northeastern test site Tuesday.
She tested its first nuclear device and tightened the state's grip over the economy.
The reclusive communist state detonated a small nuclear device in late 2007, according to U.S. intelligence officials.
On 12 February the North tested a nuclear device, which is believed to be its third such test.
Observers fear North Korea is working towards creating a nuclear device small enough to fit on a long-range missile.
Among the undeclared nuclear states, India exploded one "peaceful" nuclear device in 1974.
The primitive nuclear device tested by North Korea in 2006 is estimated to weigh more than 1, 500 kilograms (3, 307 pounds).
Security Council on Jan. 22 penalized North Korea for the launches, Pyongyang responded with threats to detonate a nuclear device.
North Korea recently tested a crude nuclear device, adding yet another member to that previously exclusive club of nuclear weapon states.
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Security Council resolutions, the latest issued last month, North Korea on Tuesday detonated a nuclear device at a remote underground site.
Ever since 1974, when India tested a supposedly peaceful nuclear device, it has had the technical wherewithal to build the bomb.
South Korea's success comes amid increased tension on the Korean Peninsula over North Korea's threat to explode its third nuclear device.
But advocates for preventing nuclear proliferation say it highlights the risk that terrorists could obtain enough fuel to build a nuclear device.
India tested a nuclear device in 1974 to counter China's nuclear arsenal.
Tensions have run high on the Korean Peninsula for months, with North Korea testing a nuclear device and its intercontinental ballistic missile technology.
This has been true even though India had not tested a nuclear device since 1974 and Pakistan is believed never to have done so.
In February, the country conducted its third underground detonation of a nuclear device, possibly using enriched uranium rather than the plutonium employed in previous tests.
After North Korea test-fired missiles in July 2006 and then exploded a nuclear device the following October, South Korea suspended grants of fertiliser in protest.
Security experts say it successfully detonated a miniaturized nuclear device in its Feb. 12 test, which followed the launch of a long-range rocket in late December.
But now that the North appears to have tested a nuclear device, Sullivan reports that newspapers are slamming Roh for what they're calling a failed strategy.
Would the mullahs be so reckless as to hide a nuclear device in a container on a ship and set it off near one of our cities?
South Korean officials have said that activity at the Punggye-ri site indicates preparations for another nuclear test after North Korea exploded a nuclear device there on Feb. 12.
South Korea's Kospi shed 1.3% amid escalating fears over North Korea, which now appears to have developed a nuclear device small enough to mount on a ballistic missile.
Of course, these sentiments were expressed by test-ban advocates in the executive and legislative branches before there was evidence that China was preparing to detonate a nuclear device.
Twenty-five countries, including Russia and China, backed the measure, which also demanded that Iran stop uranium enrichment, which can be used for producing fuel for a nuclear device.
Less than a day after North Korea tested a nuclear device, Mr Obama said the US will "lead the world in taking firm action in response to these threats".
However, we cannot overlook that we are in a race to bring about the downfall of this corrupt regime before it can achieve a nuclear weapon or nuclear device.
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