"While they said they wanted to maintain a civil nuclear program, they also acknowledged that most of their nuclear programs are weapons related," Kelly told the Senate Foreign Relations Committee in his first public briefing since returning from the third round of the talks in Beijing last month.

North Korea has refrained from stating publicly that it has nuclear weapons, although it speaks of an existing "nuclear deterrent."

Kelly said the North Korean delegation at the talks "clearly identified" a five-megawatt reactor at Yongbyon as a nuclear weapons facility.

Pyongyang began to reactivate the Yongbyon reactor after expelling International Atomic Energy Agency (IAEA) inspectors in 2002 following US exposure of its secret nuclear arms program.

North Korea had declared several times in 2003 that it had finished reprocessing its 8,000-plus existing spent fuel rods and the United States believes it could have produced enough fissile material for five or six additional nuclear weapons.

Since then, North Korea has stated it is strengthening what it calls its nuclear deterrent capability.

Kelly said North Korea proposed at the Beijing meeting it would freeze its nuclear weapons programs for rewards, including energy aid, lifting of sanctions and removal from the list of nations sponsoring terrorism.

"We are continuing to study the North's proposal," he said, pointing out that "it is clear we are still far from agreement."

At the talks, the United States offered Pyongyang three months to shut down and seal its nuclear weapons facilities in return for economic and diplomatic rewards and multilateral security guarantees.

It was the first significant overture to Pyongyang since US President George W. Bush took office in early 2001 and branded the North part of an "axis of evil" alongside Iran and pre-war Iraq.

Following concerns expressed by senators over North Korea's poor human rights record, Kelly said dismantlement of North Korea's nuclear arsenal alone would not lead to normalization of relations with the United States.

"We've made clear that normalization of our relations would have to follow these other important issues, and human rights is co-equal in importance, perhaps even more important, than conventional forces, chemical weapons, ballistic missiles, matters of that sort," he said.

Aside from the United States and North Korea, the other parties at the six-party talks were host China as well as Russia, South Korea and Japan.

Kelly said the North Korean proposal lacked detail and was vague.

Of particular concern was that the proposal had ignored the Stalinist state's pre-2003 plutonium, nuclear weapons and the uranium enrichment program.

There were also doubts on what the scope of the freeze and dismantlement would be, Kelly said, adding that inclusion of Pyongyang's uranium enrichment program in any solution was "critical."

North Korea also wanted to exclude the IAEA, the UN's nuclear watchdog, from verification and sought to create a new verification regime from among the six countries involved in the crisis talks, Kelly said.

"This unprecedented approach would be hard to set up and carry out," he said.

Kelly said among "positive elements" in positions Pyongyang staked out in the Beijing talks was that a freeze in its nuclear weapons program would be "the first step on the path to nuclear dismantlement, not an end to itself."

Pyongyang confirmed that whatever was included in the freeze would also be incorporated in any commitment to dismantlement further down the line, he said.

The fourth round of the six-party talks is scheduled to be held by the end of September.

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