North Korea performs nuclear bomb test...

Time for Obama to fire off a sternly worded letter...

SEOUL (Reuters) - North Korea conducted its third nuclear test on Tuesday in defiance of existing U.N. resolutions, angering the United States and Japan and prompting its only major ally, China, to call for calm.

The North said the test had "greater explosive force" than the 2006 and 2009 tests that were widely seen as small-scale. Its KCNA news agency said it had used a "miniaturized" and lighter nuclear device, indicating that it had again used plutonium which is more suitable for use as a missile warhead.

North Korean leader Kim Jong-un, the third of his line to rule the country, has presided over two long-range rocket launches and a nuclear test during his first a year in power, pursuing policies that have propelled his impoverished and malnourished country closer to becoming a nuclear weapons power.

U.S. President Barack Obama labeled the test a "highly provocative act" that hurt regional stability and he and other states that are members of U.N. Security Council pressed for new sanctions on the isolated country.