North Korea is pulling out of the nuclear Non-Proliferation Treaty with immediate effect but says it has no intention of developing nuclear weapons.
The communist state's official news agency is today broadcasting a government statement that accuses Washington of seeking to topple its political system yet offers the option of "separate verification" of its nuclear programme.
The North's statement rejects a call from the UN to readmit inspectors who had been monitoring a reactor capable of producing plutonium for weapons.
"The government of the Democratic People's Republic of Korea in a statement today declared its withdrawal from the nuclear Non-Proliferation Treaty (NPT) and its total freedom from the binding force of the safeguards accord with the International Atomic Energy Agency (IAEA)," it said.
"Though we pull out of the NPT, we have no intention of producing nuclear weapons and our nuclear activities at this stage will be confined only to peaceful purposes such as the production of electricity," it added, the KCNA news agency reports.
The move comes after two New York-based North Korean diplomats held talks with former UN ambassador Mr Bill Richardson. Further talks are scheduled for today.
Japan's Foreign Ministry expressed its "grave concern" at North Korea's withdrawal from the treaty. The yen fell to a three-and-a-half-year low against the euro. South Korean stocks fell on the news, and the won slipped against the US dollar.
South Korea's YTN television quoted a North Korean diplomat in Beijing as saying the North would reconsider its withdrawal from the treaty if Washington resumed shipments of oil. Washington halted the shipments after saying the North had admitted to pursuing a secret nuclear weapons programm.
Today's announcement followed an ultimatum from the Vienna-based IAEA on Monday calling on North Korea to readmit nuclear inspectors expelled last month after the North said it was restarting the reactor to produce electricity.
Some analysts say impoverished North Korea is stepping up the angry rhetoric to win concessions from the West.