The Security Council began weighing a US draft resolution to impose potentially crippling sanctions on North Korea after the secretive communist nation claimed to have set off an atomic explosion, drawing widespread international condemnation including from its closest allies.
The Security Council unanimously condemned North Korea's decision to flout its appeal not to carry out a test and urged Pyongyang to refrain from further nuclear blasts, return to six-party talks and keep its pledge to scrap its clandestine weapons program.
US President George W. Bush called the North Korean announcement provocative and unacceptable, though he said Washington is still trying to confirm the test. Nonetheless, Pyongyang's actions "constitutes a threat to international peace and security" and requires "an immediate response" from the Security Council, he said.
Soon after, US Ambassador John Bolton asked the council to adopt a very strong resolution imposing new sanctions against the North aimed at curbing its nuclear and ballistic missile programs, prohibiting all trade in military and luxury goods, and preventing "any abuses of the international financial system" that could contribute to the transfer or development of banned weapons.
The United States circulated a draft resolution late Monday that would condemn the test, demand that North Korea immediately return to six-party talks without precondition, and impose sanctions for Pyongyang's "flagrant disregard" of the council's appeal not to detonate a device. The draft, obtained by the Associated Press, was based on proposals circulated earlier Monday.
Japan's UN Ambassador Kenzo Oshima, the current council president, said all council members "emphasized that the response of the council should be strong, swift and very, very clear in its message and its action."
But just how long it will take members to agree on a resolution remains to be seen.
Council experts met Monday afternoon to start discussing the proposals, and were to meet again Tuesday morning.
It was unclear whether China and Russia _ the North's closest allies _ would support some of the tough measures. They include international inspection of all cargo to and from North Korea to limit the proliferation of nuclear, chemical and biological weapons, blanket bans on luxury and military goods, and any material that could be used in the production of weapons of mass destruction.
The U.S. draft contained tough new proposals from Japan that would ban all countries from allowing any North Korean ships in their port or any North Korean aircraft from taking off or landing in their territory. The Japanese proposals would also impose travel restrictions on high-ranking North Korean officials, create a Security Council committee to monitor implementation of the sanctions, and ask the secretary-general "to actively engage in this matter."
Before Monday's experts meeting, the ambassadors from the five veto-wielding council nations _ the U.S., Britain, France, Russia and China _ met with Japan's U.N. Ambassador Kenzo Oshima, the current council president.
Bolton told reporters afterward that everybody agreed the council should respond swiftly, but he would not speculate when that might be given the complexity of the proposal. He noted that Japan and others already had other suggestions for the text.
"The fact is that in our half-hour, full council meeting this morning, there was no one who even came close to defending this test by North Korea," Bolton said. "All agreed that it requires a strong council response, and now we have to get that down to the specifics in the text."
The United States, France, Britain and Japan want the resolution under Chapter 7 of the U.N. Charter, which deals with threats to international peace, breaches of the peace and acts of aggression. To deal with these threats or conflicts, the council can authorize a range of measures from breaking diplomatic ties and imposing economic and military sanctions to taking military action to restore peace.
Neither Russia nor China would say whether they support a Chapter 7 resolution.
"I think we have to react firmly," China's U.N. Ambassador Wang Guangya said. "But also I believe that on the other hand the door to solve this issue from a diplomatic point of view is still open."
Russia's U.N. Ambassador Vitaly Churkin said the North Koreans "will be facing a very serious attitude on the part of the Security Council and the entire international community," but he said the council needs to discuss whether that will include sanctions.
The reported test came one day after the ninth anniversary of reclusive North Korean leader Kim Jong Il's accession to power. It also came just hours before the Security Council voted by acclamation to nominate South Korean Foreign Minister Ban Ki-moon to succeed Kofi Annan as the next U.N. secretary-general. The 192-nation General Assembly is expected to approve the recommendation later this month.
Ban said one of his priorities, if approved, would be to work to resolve the North Korean crisis.
There was growing speculation in U.N. corridors that the timing of the test was aimed at showing Pyongyang's displeasure and opposition to a South Korean taking the helm of the United Nations on Jan. 1 when Annan's second five-year term ends. The North's announcement of the test came a day after Ban topped an informal poll of council members for the fourth time.
North Korea, meanwhile, kept up its defiance of the international community.
Pak Gil Yon, the North's U.N. ambassador, said the Security Council should congratulate the Democratic People's Republic of Korea, known as the DPRK, instead of passing "useless" resolutions or statements.
"The nuclear test in the DPRK will greatly contribute in increasing the world deterrence of the DPRK" and will contribute "to the maintenance and guarantee of peace and security in the peninsula and the region," he said.
The United States and its allies, and many of North Korea's neighbors, took the exact opposite view.
"This shows why we need actions and not just words about North Korea," Bolton told AP.
Although North Korea has long claimed it had the capability to produce a bomb, the test would be the first proof that it had done so.
If the test is confirmed, North Korea would join the current members of the nuclear club _ the United States, Russia, Britain, France, India, Pakistan and China. Israel is widely believed to have the bomb but has not publicly declared.
Officials worried that a nuclear armed North would dramatically alter the strategic balance of power in the Pacific, and would undermine already fraying global anti-proliferation efforts.
While voicing concerns, Japan's Prime Minister Shinzo Abe, after meeting with the South Korean leader in Seoul, called for a "calm, yet stern response." The situation marked his first major foreign policy test since his recent election.
South Korea said it had put its military on high alert, but it had noticed no unusual activity among North Korea's troops.
Bolton told the Security Council that Washington would consider an attack on Japan or South Korea an attack on the United States, according to U.N. diplomats who spoke on condition of anonymity because the remarks were made at a closed council meeting.
The United States has defense agreements with the two Asian allies and thousands of U.S. troops are stationed in South Korea and Japan.
Condemnation of the tests was largely unanimous, with both China and Russia speaking out against it and British Prime Minister Tony Blair saying it was a "completely irresponsible act."
Only Iran, which also faces Security Council action over its failure to suspend uranium enrichment _ a program it says is for peaceful purposes _ expressed understanding for North Korea's action.
Iranian state radio blamed the North's reported nuclear test on U.S. pressure, saying the test "was a reaction to America's threats and humiliation."
The North has refused for over a year to attend six-party international talks aimed at persuading it to disarm, demanding instead that the U.S. drop financial sanctions it has imposed to punish Pyongyang alleged counterfeiting and money laundering.
It pulled out of the Nuclear Nonproliferation Treaty in 2003 after U.S. officials accused it of a secret nuclear program, allegedly violating an earlier nuclear pact between Washington and Pyongyang.
Impoverished and isolated, North Korea has built up its military and nuclear programs while relying on foreign aid to feed its 23 million people since its state-run farming system collapsed in the 1990s following decades of mismanagement and the loss of Soviet subsidies.
South Korea said the nuclear test was conducted at 10:36 a.m. Monday (9:36 p.m. EDT Sunday) in Hwaderi near Kilju city on the northeast coast. South Korean intelligence officials said the seismic wave had been detected in North Hamkyung province, the agency said.
The North's official Korean Central News Agency said the test was successful, with no leak of radiation, and said this was "a stirring time when all the people of the country are making a great leap forward in the building of a great prosperous powerful socialist nation."
"It marks a historic event as it greatly encouraged and pleased the ... people that have wished to have powerful self-reliant defense capability," KCNA said. "It will contribute to defending the peace and stability on the Korean Peninsula and in the area around it."
The North is believed to have enough radioactive material for about a half-dozen bombs. It insists its nuclear program is necessary to deter a U.S. invasion _ its justification for the test.
The North has active missile programs, but it isn't believed to have an atomic bomb design small and light enough to be mounted on a long-range rocket that could strike targets as distant as the United States.
Reports about the size of the explosion were conflicting, ranging from South Korea's geological institute estimated at the equivalent of 550 tons of TNT to Russia's Defense Minister Sergei Ivanov saying it was the equivalent of 5,000 to 15,000 tons of TNT.
Only Russia said the blast was a nuclear explosion, but the reaction of world governments reflected little doubt that they were treating the announcement as fact.
A U.S. government official, who spoke on condition of anonymity because of the political sensitivity of the situation, said the seismic event could have been a nuclear explosion, but its small size was making it difficult for authorities to pin down.
The U.S. Geological Survey said it recorded a magnitude 4.2 seismic event in northeastern North Korea. Asian neighbors also said they registered a seismic event, and an official of South Korea's monitoring center said the magnitude 3.6 tremor was not a natural occurrence.
Japan dispatched three aircraft to waters between Japan and the Korean peninsula to monitor radiation levels, the Defense Agency said. Russia reported no increase in radiation levels in its Primorye territory, which borders North Korea.
The news had a predictable impact on South Korea's financial markets, with stocks plunging Monday in Seoul in a slide mirrored by that in the country's currency, the won.
Markets in South Korea, the world's 10th-largest economy, have long been considered vulnerable to potential geopolitical risks from the North. The two countries, which fought the 1950-53 Korean War, are divided by the world's most heavily armed border.
The conflict ended in a cease-fire that has yet to be replaced with peace treaty, are divided by the world's most heavily armed border. However, they have made unprecedented strides toward reconciliation since their leaders met at their first-and-only summit in 2000.