Standing firm on a key disagreement, North Korea declared Tuesday it would not relinquish peaceful nuclear energy as diplomats from six nations opened another round of stalemated negotiations on its nuclear weapons program.

"The DPRK has the right to peaceful nuclear activity," said the chief North Korean negotiator, Vice Foreign Minister Kim Gye Gwan, using the initials for his country's formal name, the Democratic People's Republic of Korea. "This right is neither awarded nor needs to be approved by others."

Kim's declaration, made to the official New China News Agency as he flew to Beijing, suggested continued difficulties in the talks despite renewed pledges from all participants to show flexibility and goodwill. The talks among China, North and South Korea, Japan, Russia and the United States are aimed at the stated goal of achieving a nuclear-free Korean Peninsula. The issue of peaceful nuclear energy was a major reason the last round was suspended Aug. 7, after 13 days of intense bargaining.

The recess was supposed to be a time of reconsideration in the six nations' capitals, particularly in Pyongyang, U.S. officials said. But Kim's statement indicated that, from North Korea's point of view, the dispute over the production of nuclear energy for electricity remains unchanged.

"If the United States tries to lay down obstacles to the DPRK's using this right, we utterly cannot accept that," the North Korean envoy stated.

President Bush, speaking to reporters in Washington about Iran, which has also declared its intent to generate nuclear power, said, "It's a right of a government to want to have a civilian nuclear program," adding that "there ought to be guidelines" for such programs.

But the Bush administration remains adamant that North Korea must abandon its nuclear weapons programs and forgo nuclear energy production. The reason, the chief U.S. negotiator said in a briefing Friday in Washington, is that North Korea in the 1990s transformed a research reactor at Yongbyon into a source of weapons-grade plutonium.

"What North Korea needs to do is get out of the nuclear business," the U.S. negotiator, Christopher Hill, said. They have "had trouble keeping peaceful programs peaceful."

The chief Japanese negotiator, Kenichiro Sasae, said North Korea's position on peaceful nuclear energy would be key to determining whether the six-party talks could move forward.

Despite Kim's apparently clear-cut declaration, Hill expressed hope that North Korea may have found a way to alter its position on that and other points since August. "We know precisely what the issues are," he told reporters here Tuesday. "I hope the DPRK delegation has also done its homework."

Chinese diplomats met with Hill and other delegations Tuesday, beginning open-ended discussions on a Chinese-drafted proposal for "agreed principles" to govern North Korea's nuclear disarmament. China has sponsored the six-party talks since they began in August 2003. The search for broad principles was launched at the last round of talks as a way to find a lowest common denominator of agreement, on which more specific accords could then be built. The idea, Hill explained, was to avoid the swift deadlock that had developed in three previous rounds by first finding agreement on broader goals.

But the fourth round bogged down in fundamental discord over peaceful nuclear energy, the timing of recognition and aid that North Korea would receive in return for giving up nuclear weapons and North Korea's desire to address the nuclear protection it says is implicit in the U.S.-South Korean alliance.