Oct. 9 (Bloomberg) -- U.S. President George W. Bush condemned North Korea's reported first nuclear test and demanded the United Nations take quick, decisive action.

Bush said North Korea's actions were ``unacceptable'' and will only raise tensions in the world and further isolate the rogue nation. The UN Security Council met in closed session in New York to craft a response.

``North Korea has defied the will of the international community and the international community will respond,'' Bush said today at the White House. ``The United States remains committed to diplomacy, and we will continue to protect ourselves and our interests.''

North Korea's announcement of a nuclear test may prod the UN to impose sanctions on Kim Jong Il's regime. The U.S. is proposing a ban on all military and luxury goods, as well as so- called ``dual-use'' industrial items that could be used for North Korea's weapons programs. The U.S. also is calling for countries to crack down on suspicious North Korean financial transactions, and for an international inspection regime to be established for all cargo in and out of the country.

The U.S. ambassador to the UN, John Bolton said he wants a so-called Chapter 7 resolution that includes the threat of military action. Chinese Ambassador Wang Guangya, while saying the UN ``must act firmly'' said ``the door to solve this issue, from a diplomatic point of view, is still open.''

Security Council Statement

North Korea's announcement came just hours after the Japanese and Chinese governments joined the Security Council in warning the communist country against conducting a test. Chinese officials notified the U.S. of the test.

North Korea's state-run news agency said the state ``safely and successfully conducted an underground nuclear test,'' and now has ``a powerful, self-reliant defense capability.''

The U.S. Geological Survey detected a tremor of magnitude 4.2, which is ``within the range'' of previous underground nuclear tests, said Bill Leith, a seismologist at the agency. Amy Vaughan, a geophysicist at the National Earthquake Information Center, said the tremor occurred in the northeastern part of the country. South Korean officials said their instruments detected tremor of magnitude 3.58 to 3.7.

White House spokesman Tony Snow said it ``could take a couple of days'' to analyze the data and confirm whether a nuclear device was detonated. Some experts said they remained skeptical about North Korea's claim.

``There are lots of questions about this test,'' said Jim Walsh, a nuclear weapons expert at the Massachusetts Institute of Technology in Cambridge who visited North Korea last year. While the tremors detected were within the range of nuclear tests, he said, they were on the lower end.

`Unusual' Test

``It's very unusual for countries that are testing for the first time to have such a small test,'' Walsh said. ``People are going to ask whether this was a failed test -- in other words, a fizzle -- of a much larger bomb that only half went off, or a fake.''

Bush said the ``claim itself constitutes a threat to international peace and security.''

The president spoke this morning with the leaders of South Korea, China, Japan and Russia, the other nations that have been engaged in negotiations with North Korea. They joined the U.S. in denouncing the action. China, the government with closest ties to Kim's regime, said the test was a sign of ``brazen'' disregard for international opinion.

`Immediate Response'

``We reaffirmed our commitment to a nuclear-free Korean Peninsula,'' Bush said. ``All of us agreed that the proclaimed actions taken by North Korea are unacceptable and deserve an immediate response by the United Nations Security Council.''

The five nations have been trying to persuade North Korea to dismantle its nuclear weapons programs since October 2002, when the Asian state acknowledged breaking a 1994 agreement to end its atomic development program.

The test, if confirmed, is the first since Pakistan and India set off devices in 1998. It ``creates serious security challenges'' for the world, said Mohammed ElBaradei, director general of the International Atomic Energy Agency.

Bush labeled North Korea a member of an ``axis of evil,'' along with Iran and Iraq, in 2002, and critics said the president's stance on talks has blocked progress.

Bush's policy of rejecting direct negotiations with North Korea has ``completely backfired,'' said Joseph Cirincione, a senior vice president for national security at the Center for American Progress in Washington. The administration ``adopted a policy of regime change where they thought they could knock off these outlaw regimes one by one,'' Cirincione said.

`Final Red Line'

``What's happened is exactly the opposite of what they promised,'' Cirincione said. ``Every single member of the axis of evil is more dangerous to the United States now.'' He cited ``chaos'' in Iraq, Iran's acceleration of its nuclear program and North Korea's crossing the ``final red line'' of a nuclear test.

Walsh, who held informal talks with North Korean officials last year in the capital, Pyongyang, about their nuclear ambitions, said he agreed that U.S. policy toward North Korea ``failed spectacularly.'' He said Bush's statement that North Korea might share its nuclear technology with terrorists or other states hostile to the U.S. is ``greatly exaggerated.''

``They do realize that sharing their technology is a red line,'' Walsh said. ``Testing may not be a red line to them but sharing would be.''

Famine

North Korea has isolated its 23 million citizens for almost 60 years under Kim Il Sung and his son Kim Jong Il, who has ruled since 1994. Under the Kim regimes, the country pursued nuclear weapons even as citizens suffered from famine in the late 1990s. Food shortages have killed as many as 2 million people, according to the U.S. Agency for International Development.

North Korea agreed at a September 2005 session of six-nation talks to abandon its nuclear program in return for energy and food aid and security guarantees.

Kim's government broke off talks a month later and said it would proceed with a nuclear test because of threats and sanctions by the U.S. The Bush administration imposed sanctions over allegations of money-laundering and counterfeiting by North Korean companies. The announcement of the test also indicates that North Korea is willing to defy the other nations as well.

``North Korea, which once listened to China, now clearly isn't listening to China and is thumbing its nose at the six- party process hosted by China,'' said Guan Anping, a former official at China's Ministry of Foreign Trade and the managing partner of Beijing-based law firm Anping & Partners.

China

Koh Yu Hwan, professor of North Korean studies at Dongguk University in Seoul, said the test ``means the end of China-North Korea relations.''

U.S. officials estimate North Korea may have produced as many as six nuclear weapons from spent reactor fuel, according to a May 25, 2006, Congressional Research Service report. The Institute for Science and International Security reported June 26 that North Korea may have enough plutonium to make as many as 13 nuclear weapons.

In addition, North Korea tested seven missiles in July, including the Taepodong-2, which U.S. officials have said may be able to reach Alaska.

North Korea's action may set off an arms race in the region similar to the nuclear proliferation in South Asia, where India detonated two devices in May 1998, followed in the same month by Pakistan's test of a bomb.

``Proof that North Korea has a working nuclear weapon will prompt Japan, South Korea and Taiwan to arm themselves with nuclear weapons,'' Koh said. ``This will inevitably threaten China, and China won't stand for that.''

To contact the reporters on this story: Roger Runningen in Washington at rrunningen@bloomberg.net; Catherine Dodge in Washington at Cdodge3@bloomberg.net.

Last Updated: October 9, 2006 17:26 EDT