North Korea's apparent test of a nuclear device could have a devastating effect on the world's long struggle to contain the spread of the most powerful military weapon known to man.

Experts have long worried that if the Pyongyang regime flaunted its atomic hardware, Asia might be drawn into an arms race reminiscent of the early days of the cold war. The spiral could develop like this: Threatened, Japan and South Korea start their own weapons programs. China piles up bombs to protect its regional superpower status. India strives to catch China, and then Paki-stan tries to counter India, and then....

But this nightmare scenario is far from inevitable, point out experts. Everything depends on what the US and other interested governments do to try to repair a nonproliferation system that, despite its faults, has served the globe well for decades.

"Now is the time for farsighted, collaborative, and smart policies to prevent the further spread and use of nuclear weapons," concludes George Perkovich, a nuclear strategy and nonproliferation expert at the Carnegie Endowment for International Peace in Washington.

Tuesday North Korea took its nuclear bluster to a new level, saying it could fire a nuclear-tipped missile unless the US agreed to bilateral negotiations.

Monday's nuclear test was "an expression of our intention to face the United States across the negotiating table," an unnamed North Korea official told South Korea's Yonhap news agency.

Most experts in and outside the US government doubt that Pyongyang has the expertise to produce a nuclear warhead small enough to fit on an intercontinental ballistic missile. North Korea was simply trying to negotiate with threats and intimidation, said John Bolton, US ambassador to the UN.

"It's worked for them before. It's not going to work this time," Mr. Bolton said.

At the United Nations Security Council, discussions resumed concerning sanctions proposed by the US. The sanctions package could include everything from international inspection of all cargo leaving or entering North Korea to a prohibition on any military trade with the reclusive Pyongyang regime.

As US officials noted, even North Korea's claim that it had exploded a nuclear device represented the crossing of a fateful threshold. If nothing else, Pyongyang had called Washington's bluff, some experts pointed out. President Bush, among others, has said in the past that the US would not "tolerate" an overtly nuclear North Korea.

Given the military difficulties of attacking a nuclear-weapon state, and of destroying stockpiles of fissile material, "tolerate" may no longer be the operative word.

"Any US statements that North Korea cannot be allowed to acquire nuclear weapons are meaningless bluster," writes Anthony Cordesman, a military expert at the Center for Strategic and International Studies, in an analysis of the meaning of the North Korean test.

At the same time, the test shows that current US policies aimed at curbing North Korea's nuclear ambitions haven't worked, says Daryl Kimball, executive director of the Arms Control Association in Washington. A new, more energetic diplomatic approach is needed – and fast, he says.

North Korea's actions could "have devastating effects on the struggle against proliferation," says Mr. Kimball.

Even before the test, current six-party talks on North Korea were stalled due to inflexibility on the part of both Washington and Pyongyang.

The US has indicated that a face-to-face meeting with North Korea might be possible in the context of these six-party negotiations. That offer should remain on the table, say some experts, despite North Korea's provocative actions.

However, in the short term, the US probably faces a period of tension and harsh words in its dealings with the unpredictable North Korean regime, says Jim Walsh, a proliferation expert at the Security Studies Program at the Massachusetts Institute of Technology in Cambridge.

Mr. Walsh, who visited North Korea last year, says that officials there continually told him that their ultimate goal is a denuclearized Korean peninsula – but that they would get nuclear weapons first, on the path toward that goal.

Thus a quick reversal of course on the part of the North Koreans may be unlikely.

"In the near term, this is not going to be undone," says Walsh.

But there are nuclear programs that have been rolled back, he notes. South Africa, among others, decided that atomic weapons were not in its national security interest.

North Korea – or, more specifically, the small cadre that runs the nation – does not so much want to be a nuclear power as to survive, says Walsh. Right now, it sees an atomic arsenal as a means to that end.

"What they really want is normalized relations," says Walsh.

Meanwhile, US policy has been inconsistent, veering back and forth between officials who want to negotiate with North Korea and those who want to squeeze it.

For now, the nuclear test is likely to strengthen the hand of US hard-liners.

"This will clarify US policy, but in a direction unlikely to yield results," says Walsh.