North Korea carried out its third underground nuclear test in defiance of United Nations sanctions and reported pressure from China, according to western diplomatic sources.
The underground blast was confirmed by South Korea’s government and reported to the United Nations.
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The underground blast took place on the eve of President Obama’s State of the Union speech, in which the president is expected to announce plans for steeper cuts in U.S. nuclear forces.
"I am certain North Korea conducted a nuclear test," said one western diplomat.
Separately, a United Nations diplomat told Reuters that South Korea’s government confirmed the nuclear test that was first detected by international seismic monitors as a 4.9 magnitude event in a remote area of North Korea.
U.S. intelligence agencies last night were trying to confirm that the seismic activity was the widely anticipated underground nuclear test promised by the communist regime in Pyongyang.
The spy agencies also are closely monitoring North Korea for additional military activity, including a possible long- or medium-range missile test.
North Korea in the past has conducted missile tests with its nuclear blasts in 2006 and 2009.
The nuclear test is expected to increase tensions on the Korean peninsula between North and South Korea.
South Korea’s chairman of the joint chiefs, Gen. Jung Seung-jo, told a parliamentary defense committee last week that South Korean military forces would risk war and launch preemptive strikes against North Korean nuclear facilities if signs were detected that the North was preparing to use nuclear weapons.
Jung stated that military doctrine toward the North calls for attacking and removing nuclear facilities rather than engaging in an all-out war and withstanding a nuclear attack from the North.
The latest nuclear test also represents a diplomatic failure for the United States, which sought to gain Chinese support for pressure on its fraternal communist ally not to conduct the test.
The State Department privately appealed to China’s government on several occasions in recent weeks to urge North Korea not to conduct the test.
The United Nations is expected to condemn the nuclear test as further destabilizing the region. Additional sanctions on North Korea could be imposed. However, past U.N. sanctions appear to have had a limited effect on the reclusive, impoverished communist state that continues to invest in developing nuclear arms and missile delivery systems.
Obama is expected to announce during his State of the Union speech before Congress that the United States will cut its declining nuclear arsenal by an additional one-third.
The United States agreed to reduce its warhead stockpile to 1,550 under the 2010 New START arms treaty. An additional 500 warheads could be cut under Obama’s new plan.
Critics of the cuts say the United States is reducing its nuclear arsenal at a time when all other nuclear powers are expanding and modernizing their arsenals.
Obama promised in 2010 that he would spend $85 billion over 10 years to modernize U.S. nuclear weapons but has not pressed Congress to provide the funds. The U.S. nuclear arsenal is aging and in dire need of upgrading both the weapons and the infrastructure required to maintain them.
The U.S. Geological Survey reported late Monday that a seismic disturbance, estimated to be the equivalent of a 4.9 magnitude earthquake, was detected in the region where North Korea was preparing for an underground nuclear test.
U.S. intelligence agencies have been closely monitoring North Korea’s nuclear test facility near Kilju, in a mountainous region of northeastern North Korea.
There were no announcements by the official Korean Central News Agency of a nuclear test as of late Monday evening.
North Korean official media in the past several weeks announced that the Pyongyang regime would conduct a nuclear test. The announcement came in response to a U.N. Security Council resolution last month condemning North Korea for its test launch of a new long-range Taepodong-2 missile.
The USGS reported that the seismic activity was detected at a depth of about 1 kilometer.
U.S. officials told the Free Beacon last week that North Korea was preparing to conduct an underground nuclear test coinciding with a political event, such as Tuesday night’s state of the union address by Obama.
The officials said North Korea is expected to conduct medium- or long-range missile tests around the time of the nuclear test, including a possible test launch of the new KN-08 road-mobile ICBM.
U.S. intelligence agencies took several days to confirm two earlier underground nuclear tests, in October 2006 and in May 2009.
Testing for a nuclear blast involves seismic monitoring stations, as well as special "sniffer" aircraft capable of detecting minute particles sent into the atmosphere in areas around a nuclear test facility.
U.S. officials say a key question is whether the latest test used plutonium to fuel the bomb, as occurred in the two previous tests, or was a new weapon based on highly enriched uranium.
The nuclear test in 2006 was assessed to have produced a yield of less than 1 kiloton, or 1,000 tons of TNT. The May 2009 test was assessed as having a yield of about 2 kilotons.
Both tests initially produced seismic readings of between 4.1 and 4.9 magnitude earthquakes.