North Korea conducted a nuclear test at an underground site in the remote northeast Tuesday, taking an important step toward its goal of building a bomb small enough to be fitted on a missile that could reach United States.
North Korea made clear that the explosion of its third atomic device — which it claimed was smaller than the ones in its previous two tests — was a warning to what it considers a hostile United States. Its actions drew immediate condemnation from Washington, the U.N. and others. Even its only major ally, China, voiced opposition.
"The test was conducted in a safe and perfect way on a high level, with the use of a smaller and light A-bomb, unlike the previous ones, yet with great explosive power," North Korea's official Korean Central News Agency said.
It was a defiant response to U.N. orders to shut down atomic activity or face more sanctions and international isolation, as well as a direct message from young leader Kim Jong Un to the United States, Pyongyang's No. 1 enemy since the 1950-53 Korean War.
KCNA said the test is aimed at coping with "the ferocious hostile act of the U.S." That's a reference to what Pyongyang said was Washington's attempts to block its right to launch satellites. North Korea was punished by U.N. sanctions after a December launch of a rocket that the U.N. and Washington called a cover for a banned missile test. Pyongyang said it was a peaceful satellite launch.
The timing was significant. The test in an underground tunnel came hours before President Obama was scheduled to give his State of the Union speech, a major, nationally televised address.
Obama said in a statement Tuesday that the test is "a highly provocative act" and promised to "continue to take steps necessary to defend ourselves and our allies."
The test also comes only days before the Saturday birthday of Kim Jong Un's father, late leader Kim Jong Il, whose memory North Korean propaganda has repeatedly linked to the country's nuclear ambitions. This year also marks the 60th anniversary of the signing of the armistice that ended the 1950-53 Korean War, and in late February South Korean President-elect Park Geun-hye will be inaugurated.
North Korea is estimated to have enough weaponized plutonium for four to eight bombs, according to American nuclear scientist Siegfried Hecker.
If the test was indeed successful, as claimed, it would take North Korean scientists a step closer to building a warhead small enough to be mounted on a long-range missile that can reach U.S. shores —seen as the ultimate goal of North Korea's nuclear program.
Still, it wasn't immediately clear to outside experts whether the device exploded Tuesday was small enough to fit on a missile, and whether it was fueled by plutonium or highly enriched uranium.
In 2006, and 2009, North Korea is believed to have tested devices made of plutonium. But in 2010, Pyongyang revealed a program to enrich uranium, which would give the country a second source of bomb-making materials — a worrying development for the U.S. and its allies.
Plutonium facilities are large and produce detectable radiation, making it easier for outsiders to find and monitor. However, uranium centrifuges can be hidden from satellites, drones and nuclear inspectors in caves, tunnels and other hard-to-reach places. Highly enriched uranium also is easier than plutonium to engineer into a weapon.
The nuclear test is North Korea's first since Kim Jong Un took power of a country long estranged from the West. The test will likely be portrayed in North Korea as a strong move to defend the nation against foreign aggression, particularly from the U.S., North Korea's longtime enemy.
North Korea's rocket launches and nuclear tests largely are seen by analysts as threats designed to force the United States to confront the issue of military tensions between the foes.
The test is a product of North Korea's military-first, or songun, policy, and shows Kim Jong Un is running the country much as his father did, said Daniel Pinkston, a Seoul-based expert on North Korea with the International Crisis Group think tank.
The test also shows North Korea is "more confident in their military technology and their military power," he said. "Now they will be emboldened as they focus on other goals."
The decision to push ahead with a test will be a challenge to the U.N. Security Council, which recently punished Pyongyang for launching the December long-range rocket. In condemning that launch and imposing more sanctions on Pyongyang, the council had demanded a stop to future launches and ordered North Korea to respect a ban on nuclear activity — or face "significant action" by the U.N.
U.N. chief Ban Ki-moon condemned Tuesday's nuclear test in a statement.
The test will likely draw more sanctions from the United States and other countries at a time when North Korea is trying to rebuild its moribund economy and expand its engagement with the outside world.
China expressed firm opposition to the test but called for a calm response by all sides.
North Korea cites the U.S. military threat in the region as a key reason behind its drive to build nuclear weapons. The two countries fought on opposite sides of the Korean War, which ended after three years with an armistice signed on July 27, 1953, not a peace treaty. The U.S. stations more than 28,000 troops in South Korea to protect the ally.
Whatever scientific advancements the North can gain from its third nuclear test, there's also an important political angle. Many analysts believe the North uses nuclear and missile tests to win greater concessions in stalled nuclear disarmament-for-aid talks.
"A third test increases uncertainty about the North's intentions and calculations," Robert Carlin, a former U.S. State Department official who has made dozens of trips to North Korea, said in a Stanford University website posting last year.
The other part of a credible North Korean nuclear deterrent is its missile program. While it has capable short and medium range missiles, it has struggled in tests of technology for long-range missiles needed to carry bombs to the United States.
North Korea isn't close to having a nuclear bomb it can use on the United States or its allies. Instead, Hecker said in the Stanford web posting, "it wants to hold U.S. interests at risk of a nuclear attack to deter us from regime change and to create international leverage and diplomatic maneuvering room."
The North Korean nuclear program has long been a worry for Washington and Pyongyang's neighbors. A nuclear crisis in the early 1990s was followed by another standoff during the early 2000s during the George W. Bush administration.
Starting in 2003, negotiators from five nations — China, Russia, Japan, the U.S. and South Korea — tried to persuade North Korea to abandon its nuclear programs with offers of aid in return.
North Korea walked away from those talks after being punished by the U.N. Security Council for an April 2009 rocket launch.
This program aired on February 12, 2013. The audio for this program is not available.