North Korea said it had developed nuclear weapons to protect itself against a US attack and would indefinitely boycott multilateral talks aimed at dismantling its atomic programs.

In a dramatic rejection of the second administration of US President George W. Bush, this communist state said it would no longer engage in the six-party dialogue over its nuclear weapons drive.

The foreign ministry statement carried by the official KCNA news agency also said the country would seek to strengthen its nuclear arsenal and accused the United States of plotting to overthrow its government.

It was North Korea's first official response to what was widely seen as a conciliatory gesture to Pyongyang from President Bush in his State of the Union address last week.

Three years ago United States denounced North Korea as part of an "axis of evil" along with Iran and Iraq. This time he avoided inflammatory language and said Washington was working closely with its allies to resolve the nuclear standoff.

North Korea said late last year it would not consider returning to dialogue until Bush had mapped out his second administration's policy towards it.

Pyongyang has boasted publicly in the past of possessing a nuclear deterrent and has vowed never to dismantle its atomic arsenal unless the United States drops its "hostile" policy.

"We had already taken the resolute action of pulling out of the (Nuclear Nonproliferation Treaty) and have manufactured nukes for self-defense to cope with the Bush administration's ever more undisguised policy to isolate and stifle the DPRK," Thursday's statement said.

It accused Washington of seeking to topple North Korea's political system at any cost and threatening it with nuclear attack.

The nuclear standoff erupted in October 2002 when the United States accused North Korea of operating a program based on highly enriched uranium, violating a 1994 arms control agreement. Pyongyang denied that charge but restarted a plutonium program.

North Korea attended three rounds of the six-nation talks, which also group China, South Korea, the United States, Japan and Russia. But it shunned a fourth round set for last September, complaining of hostile US policies.

The other parties to the nuclear talks with Pyongyang all expressed their dismay at Thursday's announcement, urging the country to reconsider.

Japanese Prime Minister Junichiro Koizumi said Tokyo would also keep trying to get the negotiations to resume, while Russia urged North Korea not start a new nuclear arms race.

China's foreign ministry simply said it hoped that talks with North Korea would continue, in a statement carried by the official Xinhua news agency.

North Korea's incendiary announcement also drew an immediate response from the United Nations, as well as from the European Union and major European nations.

PHOTO CAPTION

The Yongbyon-1 nuclear power plant is shown in North Korea in this International Atomic Energy Agency file photograph from May 1992. (Reuters)