The United States said Tuesday that a North Korean nuclear test would further isolate Pyongyang and pledged to work with allies to discourage "such a reckless action."
"A provocative action of this nature would only further isolate the North Korean regime and deny the people of the North the benefits they so rightly deserve," State Department spokesman Sean McCormack said in a statement.
Such a test, he said, "would pose an unacceptable threat to peace and stability in Asia and the world."
His comments came in response to a North Korean announcement 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.
The U.S. ambassador to the United Nations, John Bolton, told The Associated Press on Monday that the U.S. would bring up North Korea's statement for discussion Tuesday morning in a regular meeting of the U.N. Security Council.
Pyongyang has said it has nuclear weapons, but 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.
International efforts to persuade the North to give up its nuclear programs have been stalled since November.