SEOUL North Korea ordered U.N. inspectors to leave on Tuesday after saying it would quit international nuclear disarmament talks and restart a plant that makes bomb-grade plutonium, the United Nations said.
Secretary of State Hillary Clinton strongly criticized the expulsions and said she hoped the United States and its allies could discuss it with the North.
"We are viewing this as an unnecessary response to the legitimate statement put out of concern by the Security Council," Clinton told reporters in Washington.
The U.N. Security Council on Monday unanimously condemned North Korea's rocket launch on April 5 as contravening a U.N. ban and demanded enforcement of existing sanctions.
"Obviously we hope that there will be an opportunity to discuss this not only with our partners and allies but also eventually with the North Koreans," added Clinton, who was set to meet a senior Chinese official in Washington.
North Korea said in a statement the U.N. action and separate six-country nuclear talks were an infringement of its sovereignty and it "will never participate in the talks any longer nor ... be bound to any agreement."
The statement, carried by the official KCNA news agency, said North Korea would "bolster its nuclear deterrent for self-defense in every way."
The United Nations' nuclear watchdog, the International Atomic Energy Agency, said North Korea had ordered U.N. inspectors to leave the reclusive communist country.
"(North Korea) has today informed IAEA inspectors in the Yongbyon facility that it is immediately ceasing all cooperation," IAEA spokesman Marc Vidricaire said in a statement issued in Vienna.
White House spokesman Robert Gibbs said, "North Korea will not find acceptance by the international community unless it verifiably abandons its pursuit of nuclear weapons."
Experts said the poor, energy-starved North lacked the technology to make an advanced light-water reactor.
Financial markets in Seoul and Tokyo were not affected by North Korea's announcement, with investors seeing it as more of the saber-rattling they have come to expect from Pyongyang.
North Korea began taking apart its Soviet-era Yongbyon nuclear plant more than a year ago as a part of a disarmament-for-aid deal it reached with China, Japan, Russia, South Korea and the United States.
The U.N. response to a launch widely seen as a disguised test of a long-range missile will have little immediate impact on the North's faltering economy and the divided international reaction could embolden leader Kim Jong-il, analysts said.
As well as the United States, Japan and Russia also urged North Korea to return to the often-stalled nuclear talks.
But China, which shares a border with North Korea and is the closest thing Pyongyang can claim as a major ally, called on all parties to "pay attention to the broader picture" and exercise "calm and restraint."
A Foreign Ministry spokeswoman said Beijing still hoped to achieve the denuclearization of the Korean peninsula through dialogue and negotiations.
Experts said the North could have its plant that separates plutonium from spent fuel rods up and running again in as little as three months.
Announcements like this from North Korea are part of a familiar pattern of behavior, and as such it is not likely to be a destabilizing factor for regional economies.
"Market players have come to view belligerent North Korean statements as bargaining ploys that are not to be taken at face value," said Tim Condon, an economist at ING Financial Markets in Singapore.
Chinese officials had originally called for restraint over the North Korean rocket launch. However, by subsequently joining the U.N. condemnation, Beijing has stoked uncertainty about how it intends to balance ties with Pyongyang against pressure from regional powers.
New U.N. measures may cause Beijing to curb trade in a few items but it will keep its flow of energy, grains and other materials that prop up the North's broken-down economy.
The U.S.-authored statement, agreed by the five permanent Security Council members and Japan, ordered a committee to begin activating financial sanctions and an arms and limited trade embargo laid down in a resolution 2 1/2 years ago.
North Korea's leader has basked in patriotic glory stemming from the launch in his state's propaganda, which has helped him return to the limelight after a suspected stroke in August raised questions about his grip on power.
(Additional reporting by Chris Buckley and Lucy Hornby in Beijing, Sue Pleming in Washington, Yoo Choonsik, Kim Junghyun and Rhee So-eui in Seoul, Linda Sieg in Tokyo; Writing by Ralph Gowling; Editing by Doina Chiacu)