The United States is urging the U.N. Security Council to react promptly to North Korea's threatened nuclear weapons test. The Council discussed the matter, but took no immediate action.

Within hours of North Korea's announcement that it would conduct nuclear weapons tests, Washington's U.N. Ambassador John Bolton went to the Security Council asking for a response. He called the Pyongang's move "a grave threat", and a "test case" for the world body.

"We talk a lot in the Security Council and here in New York about preventive diplomacy. But it seems to me if there were a possible test case to engage in preventive diplomacy, considering this threat by North Korea would be an excellent example," he said.

The council responded to a flurry of North Korean missile tests in July with adoption of Resolution 1695. That measure demands that Pyongyang suspend all activities on ballistic missile programs, and bans imports or exports of North Korean missile-related items.

The Council did not immediately respond to the latest North Korean threat. No statement was issued. Ambassadors agreed to meet again Wednesday to consider a strategy. But Bolton cautioned that the Council's silence should not be seen as a lack of resolve.

"Not that the North Korea should take that silence for acquiescence," he noted. " North Korea should be more concerned about silence from the Security Council today than if we had issued a four-sentence press statement because I hope it indicates that we will take very seriously what we said in Resolution 1695, about North Korea's programs in weapons of mass destruction and ballistic missiles."

China's U.N. ambassador, Wang Guangya, urged all parties to exercise restraint, and called for a resumption of the six-party talks involving North and South Korea, Japan Russia, China and the United States.

North Korea walked away from the talks nearly a year ago, and the Chinese envoy expressed doubt that the Security Council could act effectively until the six-party talks resume.

"We have to work to make sure this process will be resumed, because I think the six-party talks is the best channel," he said. "This is the position of all sides, including all of the six countries. If the six-party talks cannot do anything about it, then I don't think the council is in a [position] to do it. We have to discuss it tomorrow."

Russia's U.N. ambassador, Vitaly Churkin, said Wednesday's Council meeting would be a "brainstorming session" aimed at formulating a coherent strategy.

North Korea has long maintained that it has a nuclear arsenal, but no known tests have been conducted. In its latest statement, the Pyongyang government says it is being "compelled" to test a nuclear device because of U.S. pressure.