U.S. Secretary of Defense Donald Rumsfeld says North Korea's claim that it has nuclear weapons is "worrisome" because of the country's leadership and its history of proliferation. Mr. Rumsfeld met with defense ministers from NATO countries and Russia on Thursday.

Secretary Rumsfeld says he does not necessarily believe North Korea's claim to have nuclear weapons. He says some countries' intelligence services have reported the same thing, but he has not seen confirmation.

But if it is true, Mr. Rumsfeld says it is a matter of concern. "Given their dictatorial regime, and the repression of their own people, one has to worry about weapons of that power in the hands of leadership of that nature," he said. "I don't think that anyone would characterize the leadership in that country as being restrained."

Secretary Rumsfeld says aside from possibly using its claimed nuclear weapons, North Korea is a threat because it has demonstrated its willingness to spread dangerous technology, in violation of international rules accepted by most countries.

"Obviously, a country that has a behavior pattern that North Korea does of probably being one of the world's leading proliferators of ballistic missile technology, for example, is a sense in the sense of proliferating, and that is a worrisome thing," he said.

Secretary Rumsfeld says North Korea has broken agreements it made with countries that have been trying to negotiate an end to its nuclear weapons program. North Korea had agreed to a framework for discussing its nuclear program with the United States, Russia, China, Japan and South Korea.

Russia's Defense Minister, Sergei Ivanov, who met with Mr. Rumsfeld and other NATO defense ministers here Thursday, also expressed concern about North Korea's announcement.

"If the leadership, that is the government of North Korea, took the decision to withdraw from the six-sided negotiations I believe that such a step would have been regrettable, would have not been right, if, in fact, that is the case," he said.

Many nuclear experts believe North Korea has produced enough nuclear material for a crude bomb, and could deliver it on a missile to Seoul or Tokyo. The capability would also pose a new threat for the 37,000 U.S. troops in South Korea to deter any attack from the North.