The North Koreans' reported nuclear explosion Monday is critical to Northeast Asia and worldwide efforts to restrain nuclear proliferation. It is less important to the United States, and there is no reason for it to become a major issue for either party in the November elections.

The test explosion, which North Korea had warned a week before that it intended to carry out, puts it on the threshold of the group of countries that possess nuclear arms. These include China, France, Russia, the United Kingdom and the United States, all of which have signed the Nuclear Non-Proliferation Treaty. North Korea signed the treaty, but withdrew from it in 2003. Also possessing nuclear arms are India, Israel and Pakistan, none of which have signed the NPT. Non-nuclear weapons states that have signed the treaty permit inspections of their nuclear facilities by the International Atomic Energy Agency; nonsignators don't.

The risk now is that North Korea's neighbors, specifically Japan and South Korea, may feel obliged to proceed with their own nuclear weapons programs. No one doubts for a minute that Japan, with the world's second-largest economy and highly sophisticated technology, and South Korea, in 10th place with comparable skills, could quickly move to produce nuclear weapons. Both have signed the NPT, and yesterday Japan's prime minister said his country had no intentions of seeking atomic weapons.

The question for the United States is, could it have prevented the North Koreans from proceeding with a nuclear weapons program? The answer is probably yes. The latest U.S. approach to the problem was to engage North Korea in six-power talks, along with China, Japan, Russia and South Korea. That made sense -- dealing with what was basically a regional problem within a group of the region's powers.

But it didn't work. North Korea continued to insist on direct, bilateral talks with the United States, as well. It had several reasons for that: President Bush's inclusion of North Korea in the "axis of evil" countries, along with Iran and Iraq; continuing threats against North Korea made by senior administration officials, and the U.S. attack on Iraq that brought about the fall of the Saddam Hussein regime. As a result, Pyongyang wanted a firm pledge from the United States that it did not plan a comparable fate for the Kim Jong Il regime.

Six-power talks on the nuclear program were fine, but how was the North to know that the United States wouldn't raise the ante by forcing its government to step down, particularly with 30,000 U.S. troops stationed in South Korea? For security against that, North Korea wanted high-level talks followed by joint communiques and the like. Unfortunately, the Bush administration continued to refuse and, in the meantime, said North Korea had to give up its nuclear option first.

Then the nuclear test occurred Monday. The United States is now pursuing economic and other sanctions against North Korea within the U.N. Security Council. If they are passed, China and Russia will make sure their effect is relatively harmless to North Korea. However, further isolation of an already paranoiac North Korean regime serves no purpose.

What the United States should have done when North Korea threatened its test was to announce a willingness to dispatch Secretary of State Condoleezza Rice, or an equally credible representative, to Pyongyang to talk. Countries such as North Korea, Iran and, before the invasion, Iraq, should not have to "deserve" to talk with senior U.S. officials. Diplomatic talks are classically how leadership heads off undesirable events such as nuclear tests.