In comments attributed to a spokesman for its Foreign Ministry, North Korea said it would "open its nuclear deterrent to the public as a physical force."

In Washington, Secretary of State Colin Powell said: "They have said things like this before. I just don't know if they mean it."

Nevertheless, the remarks from Pyongyang were the strongest indication yet that North Korea, which is believed to have one or two bombs and is suspected of building more, would test a weapon to prove itself a nuclear power.