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Negotiations aimed at ending North Korea's nuclear weapons aspirations resumed Tuesday after a monthlong recess, but prospects for progress were uncertain as Pyongyang (search) remained insistent on its right to a civilian atomic program.

Envoys from China, Japan, Russia, the United States and the two Koreas gathered at a state guesthouse in Beijing to continue the fourth round of talks since 2003 on the issue. Last month, negotiators took a break after a record 13 days of meetings failed to yield an agreement on a statement of principles to lay the foundation for the North's disarmament.

No end date has been set for the talks.

North Korea's demands for a civilian nuclear program are a sticking point. Washington says the North's record proves it can't be trusted with any atomic project.

Chief North Korean negotiator Kim Kye Gwan said his country will not tolerate any obstruction to its right to a peaceful nuclear program, China's official Xinhua News Agency (search) reported.

"This right is neither awarded nor needs to be approved by others," Kim said in Pyongyang. "If the United States tries to set obstacle to (North Korea's) using this right, we can utterly not accept that."

Still, Kim said the North would attend the talks with a sincere and flexible attitude, according to Xinhua.

U.S. Assistant Secretary of State Christopher Hill said Monday upon arrival in Beijing that he wasn't sure how long the talks would last, but would know more after contacts with the North Koreans. No one-on-one meetings between the sides were planned, but Hill said he expected to speak with the North at a dinner for all delegates Tuesday evening.

"I know that my delegation is coming here to work. We know pretty precisely what the issues are. I hope the (North Korean) delegation has also done some homework," Hill said.

U.S. and North Korean diplomats met twice in New York in the past month, but Hill said there had been no progress on resolving the impasse beyond gaining an understanding of the North's position. But he said "their position does seem to be evolving a little," without elaborating.

Last week in Washington, Hill reiterated a set of measures — including energy aid offered by South Korea — that he said would make it unnecessary for the North to pursue nuclear energy. The North "has had trouble keeping peaceful programs peaceful," he said Friday.

South Korea's chief negotiator urged envoys to be open-minded at the talks.

"If each party can be a little more flexible in its position there will be good results, but if they stick to their current position, good results will be hard to expect," South Korean Deputy Foreign Minister Song Min-soon said as he arrived in Beijing.

Kenichiro Sasae, Japan's top envoy, said it was important first that the North "shows its determination in detail regarding dismantlement of their nuclear programs."

"If this happens, I think it is possible that we could be more flexible in discussing the interests that North Korea has as the next step," he said.

China and Russia are also participating in the negotiations.

The latest nuclear standoff was sparked in late 2002 after U.S. officials accused North Korea of running a secret uranium enrichment program in violation of an earlier deal, in which the North had agreed to stop weapons development in exchange for energy aid.

The North has since denied having a uranium enrichment program, which would provide a way to create radioactive material for bombs, other than its publicly acknowledged plutonium program.

On Tuesday, the North called the uranium allegations "a concoction cooked up by the United States."

"It is a very haughty, politically motivated act for the United States to circulate this kind of false view" while entering the talks," the North's main Rodong Sinmun newspaper said in a commentary carried by the country's official Korean Central News Agency.

Pakistani President Gen. Pervez Musharraf (search) told The New York Times in its Tuesday edition that he believed North Korea had obtained "probably a dozen" centrifuges — equipment needed to enrich uranium — from a network headed by a Pakistani nuclear expert.

However, hundreds of centrifuges are required to enrich enough uranium for a bomb. Some experts have said the North has acknowledged researching how to enrich uranium to lower levels that could be used to generate power and remedy its electricity shortages.

Musharraf also said the results of nearly two years of interrogations of A.Q. Khan, the father of Pakistan's nuclear bomb program, didn't yield any evidence that Khan gave North Korea a Chinese-originated design for a nuclear weapon, The Times said.