The United States has not ruled out taking military action against North Korea, the Pentagon has said.
North Korea yesterday told the US that it had finished reprocessing used nuclear fuel into bomb-grade plutonium.
In what amounted to another threatening move by Pyongyang in its standoff with Washington, North Korean diplomats at the United Nations informed their US counterparts last week that reprocessing of spent nuclear fuel rods has been completed.
"Now this is something that we are evaluating. As you know North Korea has made a lot of claims in the past and it's not something at this time that we can confirm the accuracy of," White House spokesman Mr Scott McClellan said.
Pentagon spokesman Mr Lawrence Di Rita did not answer directly when asked whether the United States was moving closer to hostilities with North Korea.
"Let me just say: the situation with North Korea is a serious situation and it's something that we should take seriously. And it's a problem not for the United States, it's a problem for the world," he said.
Asked about planning for possible military action by the United States, Mr Di Rita said: "I can't rule something in or out of the president's mind. At the moment, he is focused on diplomatic activities, and that's what we're going to be doing."
North Korea had 8,000 spent fuel rods as part of a plutonium-based nuclear weapons program at the Yongbyon nuclear site that was frozen under a 1994 nuclear deal between North Korea and the United States.
Analysts believe if those fuel rods were efficiently converted, they could produce enough plutonium for a half-dozen nuclear weapons. The CIA believes North Korea already has one or two nuclear weapons.
The United States went to war against Iraq over Saddam Hussein's yet-to-be-found weapons of mass destruction. But so far Washington still wants a peaceful solution leading to North Korea's verifiable dismantling of its nuclear weapons program, while not ruling out a military option.
"We are continuing to seek a diplomatic solution through a multilateral approach working with China and South Korea and Japan and others to address the situation in North Korea," Mr McClellan said.
Former Defense Secretary William Perry warned that the United States and North Korea are drifting toward war, perhaps as early as this year. "I think we are losing control," of the situation, Perry told the Washington Post.
Washington wants multilateral talks while Pyongyang demands bilateral talks with the United States before any multilateral discussions.