The United States warned North Korea that conducting a second nuclear test "would not be a good thing" and pressed US partners to prepare a tough response if Pyongyang does so.
"It would not be a good thing for them, but it certainly would not be out of character," White House spokesman Tony Snow said of the prospects for such a test as US Secretary of State Condoleezza Rice headed to Asia and Russia.
Asked to elaborate, Snow noted that the UN Security Council had unanimously adopted sanctions on North Korea after a first test on October 9 and added that if North Korean leaders "believe that somehow people are going to give them a pass on this, they're going to find out that they're wrong."
Snow also shrugged off Pyongyang's announcement, in one of its harshest statements in years, that it viewed UN sanctions imposed after the first test as "a declaration of war" and that it was ready for battle.
"I don't think North Korea has declared war. I think what it did is it tried to characterize the UN resolution as an act of war, which it is not," the spokesman told reporters.
Asked about the prospects for a second test, Snow declined to discuss US intelligence matters but added: "Well, let me put it this way: The North Koreans have made no secret of their desire
to be provocative."
"The first test, while nuclear, did have a low yield, and perhaps it would not be unreasonable to expect that the North Koreans might want to try something again -- once again, to be provocative," he said.
"I think it is reasonable to expect the government of North Korea will do what it can to test the will, the determination
and the unity of the United Nations, the United Nations Security Council, and the other members of the six-party talks," he said.
Those negotiations, stalled since November 2005, group China, Japan, North and South Korea, Russia and the United States in an effort to end concerns about Pyongyang's nuclear weapons programme.