Test would be serious provocation: US

Washington: US and South Korean intelligence detected a seismic event at a suspected nuclear test site in North Korea, the White House said Monday, a few hours after North Korea claimed it had conducted an underground nuclear test.

“At this point we are not confirming a nuclear test,” said White House spokesman Tony Snow.

"A North Korean nuclear test would constitute a provocative act in defiance of the will of the international community and of our call to refrain from actions that would aggravate tensions in Northeast Asia," Snow said.

"We expect the UN Security Council to take immediate actions to respond to this unprovoked act," Snow said. “The United States is closely monitoring the situation and reaffirms its commitment to protect and defend our allies in the region.”

Snow said US national security adviser Stephen Hadley informed President George Bush about the event.

Snow declined to speculate on a possible US response to a North Korean nuclear test. "At this point we're still assessing the data and trying to figure out what happened," he said. "A lot of this hinges on what the data tells us."

In a statement, House Speaker Dennis Hastert, R-Illinois, called the reported test as "a desperate act of a criminal regime."

"We are neither threatened nor impressed, but resolved to restore stability to the Pacific Rim," Hastert said. "We stand with President Bush and the international community in condemning North Korean Leader Kim Jong-il's reckless decision, and we will provide whatever assistance we can to bring this matter to a stable resolution."

"The United Nations and in particular our allies in the Pacific region must take decisive action to isolate this regime against this provocative move."

US intelligence has been closely watching several sites in North Korea that could be used for a nuclear test. Movements of people, automobiles, fencing and other items convinced some analysts last week that a test could come soon. Guest quarters overlooking one site were also of interest.

Over the last week, U.S. officials have been anticipating news of a nuclear weapons test in North Korea.