WASHINGTON (AP) – The Bush administration said Tuesday that a North Korea nuclear test would be an “unacceptable threat to peace and stability” and further isolate Pyongyang from the rest of the world.

State Department spokesman Sean McCormack said America will work with its allies to discourage “such a reckless action.” In nearly identical comments, he and Frederick Jones, spokesman for the White House’s National Security Council, warned that any such test “would only further isolate the North Korean regime” and deny North Koreans possible benefits they might reap by returning to negotiations about their nuclear program.

America and other countries have imposed financial sanctions on Pyongyang.

North Korea announced Tuesday that it would conduct a nuclear test in the face of what it claimed was “the U.S. extreme threat of a nuclear war.” The statement from Pyongyang gave no precise date as to when a test might occur.

Pyongyang has said it has nuclear weapons, but it has not conducted any known test to prove its claim. South Korea’s spy agency has said the North could test a nuclear bomb at any time.

Many experts believe the North has enough radioactive material to build at least a half-dozen or more nuclear weapons.

“They are an active proliferator,” said Secretary Rumsfeld. “And were they to test and were they then to proliferate those technologies we’d be living with a proliferator and obviously we’d be living in a somewhat different world.”

Mr. Rumsfeld, in Managua, Nicaragua, for meetings with Central and South American foreign ministers, declined to say whether Pyongyang’s announcement had triggered any changes in the American alert status.

A North Korean nuclear test, Mr. McCormack said, “would pose an unacceptable threat to peace and stability in Asia and the world.”

America and its allies have been trying to lure the North back to stalled international efforts to persuade Pyongyang to scrap its nuclear weapons program. The communist-led nation alarmed the world when it test-fired seven missiles in July, including one believed to be capable of reaching America.

The North has pushed for direct talks with America, something Washington says it will not do outside of the framework of the stalled six-nation talks. The North has refused to return to the disarmament talks because of American financial restrictions imposed for its alleged illegal activity, including money laundering and counterfeiting.

The American ambassador to the United Nations, John Bolton, told The Associated Press on Tuesday that America would bring up North Korea’s statement for discussion in a regular meeting of the U.N. Security Council. The Council is expected to talk about it on Wednesday.

Mr. Bolton said the Council should embark on “preventive diplomacy” and not just a “knee-jerk reaction” to the North Korean threat.

Vice Adm. John Morgan, the Navy’s chief of strategy and plans, told reporters that a possible test is “something we’re very concerned about. We think there needs to be a diplomatic solution to this. We think the international community is working hard to achieve that.”

Robert Einhorn, a former assistant secretary of state for nonproliferation, said that the North’s comments should be taken seriously.

“They often don’t bluff. They tell you what they’re going to do, and then they do it,” Mr. Einhorn said. “It’s a reflection of their frustration, that their previous provocations haven’t had the desired effect of getting the U.S. to talk with them bilaterally or getting the U.S. and the others to make further concessions.”