Deputy Chinese foreign minister Zhou Wenzhong in an interview with the New York Times published Wednesday said he doubted US claims that North Korea had an enriched uranium program and urged Washington to stop using the allegations to hold up nuclear talks.

He said the United States had yet to persuade China that North Korea had both uranium and plutonium programs to develop fuel for nuclear bombs.

The US State Department described Zhou's statement as "puzzling.

"We saw the story and, frankly, we find the assistant foreign minister's comments somewhat puzzling," State Department spokesman Richard Boucher told reporters.

"We have made clear over time that there is very conclusive information that North Korea has a covert uranium enrichment program," he said.

North Korea had itself acknowledged previously that it was pursuing uranium enrichment, Boucher said.

"They have asserted their so-called right to develop nuclear weapons," he said.

Boucher cited recent revelations by Pakistani scientist Abdul Qadeer Khan about North Korea's pursuit of nuclear weapons.

Khan, a one-time national hero credited with making Pakistan a nuclear power, has admitted selling nuclear secrets abroad and to assisting North Korea's nuclear enrichment program.

"So, certainly there can be no doubt that North Korean's nuclear activities represent a clear threat and they violate several important international agreements as well as the commitments that North Korea has made in the past," Boucher said.

He pointed out that it was up to the North Koreans to demonstrate that they were willing to "completely and irreversibly abandon their nuclear programs through a verifiable dismantlement of all the elements of those efforts."

North Korea has acknowledged having a plutonium program but denies that it is enriching uranium to make nuclear fuel.

"We know nothing about the uranium program," Zhou told the New York Times. "We don't know whether it exists. So far the US has not presented convincing evidence of this program."

China is hosting key talks to resolve the nuclear crisis in the Korean peninsula.

It had hosted two rounds of six-party talks on North Korea's nuclear program and is preparing to convene a third.

Zhou's comments represent a potentially important shift in Beijing's approach to the talks, which China has sought to keep afloat despite scant evidence of progress, the New York Times said.

Though China has longstanding ties to North Korea, it had previously adopted a strongly neutral position in the negotiations, which have now stretched over a year, the newspaper said.

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