After Tuesday's nuclear test, questions arose as to whether or not North Korea has advanced to the point where they could reach the continental U.S. with a missile.
An unapologetic North Korea declared Tuesday that it had conducted a test of a nuclear bomb after the detonation was detected by the U.S. Geological Survey.
"On February 12th... we successfully conducted a third underground nuclear test in the northern underground nuclear test site," the Daily NK reported, in a translation of Pyongyang's announcement on the state-run news agency, KCNA.
By conducting the test, the isolated authoritarian regime made good on a Jan. 24 pledge by North Korea's top military organ, the National Defense Commission, in further defiance of admonitions from the international community to cease and desist in its pursuit of nuclear weapons.
The test was met with condemnation from around the globe. The White House called it a "highly provocative act" that warrants "further swift and credible action from the international community." Chinese Foreign Minister Yang Jiechi said Beijing was "strongly dissatisfied and resolutely opposed" to the move by its neighbor and long-time Communist ally.
South Korea and Japan convened emergency meetings of their top national security officials, while the UN Security Council held an emergency meeting Tuesday, after which it promised to "begin work immediately" to draft a new resolution against the North.
The explosion was registered as a 5.1-magnitude seismic event by the USGS at 9:57 p.m. ET Monday. The U.S. Office of the Director of National Intelligence quickly judged that North Korea had "probably conducted an underground nuclear explosion" with a yield of "several kilotons."
In a statement, President Barack Obama said the test "undermines regional stability, violates North Korea's obligations under numerous United Nations Security Council resolutions, contravenes its [international] commitments … and increases the risk of proliferation" in the wake of what he described as a "ballistic missile launch" by North Korea on Dec. 12.
"North Korea's nuclear weapons and ballistic missile programs constitute a threat to U.S. national security and to international peace and security," Obama said.
U.S. officials have previously told NBC News that North Korea has up to a "few dozen" nuclear weapons that could be fitted on ballistic missiles, far more than had previously been believed.
Obama on Tuesday said that "the danger posed by North Korea's threatening activities warrants further swift and credible action by the international community," adding that the U.S. would work with the international community to "pursue firm action."
'Vile hostile acts'
In a tit-for-tat that has characterized a diplomatic stalemate for decades, North Korea blamed the United States for forcing its hand.
"This nuclear test was conducted as part of measures to safeguard the country’s security and independence in order to deal with the vile hostile acts of the United States, which violated our Republic’s legitimate right to peaceful satellite launches,” according to the KCNA report.
The comment refers UN Security Council Resolution 2087, passed after to Pyongyang's Dec. 12 rocket launch, heaping sanctions on previous sanctions against North Korea, further deepening the regime's isolation.
North Korean soldiers stand guard on the river bank of the North Korean town of Sinuiju, opposite the Chinese border city of Dandong on Tuesday.
The resolution called on North Korea to abandon its nuclear program and any weapons and allow verification; to conduct no more launches using ballistic missile technology; and to conduct no more nuclear tests.
U.N. Secretary-General Ban Ki-moon said the latest test was a "clear and grave violation."
Later, South Korea's Yonhap News Agency reported that North Korea threatened, citing an unidentified foreign ministry spokesman, to conduct more nuclear tests if the U.S. moves to penalize it for Tuesday's test.
At a disarmament forum in Geneva on Tuesday, a North Korean official said that his country would not change course in the current climate, Reuters reported.
"The U.S. and their followers are sadly mistaken if they miscalculate the DPRK would respect the entirely unreasonable resolutions against it. The DPRK will never bow to any resolutions," Jon Yong Ryong, first secretary of North Korea's mission in Geneva, told the Conference on Disarmament, referring to the Democratic People's Republic of Korea (DPRK).
South Korea's government said in a statement that Tuesday's nuclear test, "poses a direct challenge to the whole international community as well as an unacceptable threat to the peace and security of the Korean Peninsula and Northeast Asia."
It said the government would stand firm in that it "will not tolerate a nuclear North Korea" and added that it will "also accelerate expanding its military capability, including deploying at an early stage its extended-range missiles, currently being developed, which cover all of North Korea."
Major hostilities in the 1950-1953 Korean War ended with armistice, not a peace treaty. Today, North Korean forces and South Korean forces bolstered by about 28,000 U.S. troops remain faced off at the 38th parallel, where the Korean Peninsula was divided.
Between 2003 and 2007, North Korean took party in several rounds of the so-called "Six Party Talks" with South Korea, China, the United States, Russia and Japan, in an attempt to reverse Pyongyang's nuclear weapons development in return for fuel and progress towards normalization of relations. The talks went on hold and then fell apart for good in April 2009 and Pyongyang expelled UN inspectors from the country.
A key unanswered question is what Beijing will do after North Korea's latest move. The long-time Communist ally and neighbor, which has strategic reasons to continue supporting the regime in Pyongyang, nonetheless expressed its strong opposition to the test.
"China has been humiliated," according to Andrei Lankov, a veteran analyst of North Korea based in Seoul's Kookmin Unversity. That could prompt a change in Beijing's approach, he said.
A North Korean flag flies above the North Korean embassy in Beijing on Feb. 12.
"This time, China explicitly warned North Korea against conducting the test, but they were ignored," Landov added. "A Chinese government newspaper said two weeks ago that in the case of a nuclear test, China might significantly reduce its aid to North Korea."
China is a major source of aid to North Korea and key to keeping its decrepit economy afloat. China is also one of five permanent members of the UN Security Council with the power to veto sanctions.
The United States and other countries have urged China to put pressure on Pyongyang, but it remained to be seen how far Beijing would go to confront its old comrade.
"They are not happy about nuclear adventurism. At the same time though, a collapsing non-nuclear North Korea is far worse than a nuclear but stable North Korea," Lankov said.
North wants U.S. recognition
Professor Yan Xuetong, a top international security analyst at China's Tsinghua University, said "the key to the North Korean nuclear challenge is in the hands of the United States, not China."
"China is certainly opposed to North Korea's latest nuclear test and opposed to North Korea becoming a nuclear power, but the test was aimed at the Unite States with the aim of forcing the U.S. to normalize relations with North Korea, but if the U.S. doesn't want to play the game of trade-off, then there is not much that China can do," he said.
Yan, who closely follows government policy thinking on the issue, argued that "the role of economic sanctions is limited," suggesting China will not stop economic assistance to North Korea because of the latest test.
"What China should do is to act as bridge between North Korea and the United States so that they will agree to a trade-off, with the U.S. granting recognition to the North Korean government in exchange for it giving up its nuclear program," he said.
"If the U.S. views North Korea's nuclear threat with the same seriousness as it views Iran's nuclear threat, then there will be hope for solving the North Korea's nuclear problem," he said.
NBC News staff writers Ian Johnston, Eric Baculinao, John Newland and Arata Yamamoto contributed to this report.
This story was originally published on Tue Feb 12, 2013 12:11 PM EST