|The latest claims follow the release of satellite images showing construction of a new reactor [Reuters/DigitalGlobe]
An American nuclear scientist says he has seen hundreds of centrifuges in a sophisticated new atomic facility in North Korea this month.
Siegfried Hecker of Stanford University wrote in a report published on Saturday that he was taken during a recent trip to North Korea's main Yongbyon atomic complex to a facility with a small industrial-scale uranium-enrichment facility.
"Instead of seeing a few small cascades of centrifuges, which I believed to exist in North Korea, we saw a modern, clean centrifuge plant of more than a thousand centrifuges, all neatly aligned and plumbed below us," he said.
Hecker, who is also the co-director of the Centre for International Security and Co-operation, described the control room as "astonishingly modern", writing that, unlike other North Korean facilities, it "would fit into any modern American processing facility".
The New York Times earlier said that Hecker was told by North Korean officials they had 2,000 centrifuges operating. He told the newspaper that he had already privately informed the White House of his findings.
Hecker said he was forbidden from taking photographs and could not verify North Korean claims that the plant was already producing low-enriched uranium.
A US team that visited the country was also unable to verify North Korea's claims.
US allies briefed
While the existing ageing reactor at Yongbyon has supplied plutonium for North Korea's nuclear weapons, light-water reactors are generally used for generating electricity.
The New York Times said the White House started to brief allies and legislators on Saturday about Hecker's revelations.
Hecker, a former director of the US Los Alamos Nuclear Laboratory who is regularly given rare glimpses of the North's secretive nuclear programme, acknowledged that it was not clear what North Korea stood to gain by showing him the formerly secret area.
The revelation could be designed to strengthen the North Korean government as it looks to transfer power from leader Kim Jong-il to a young, unproven son.
North Korea expert's analysis
Leonid Petrov of the University of Sydney reacted to the latest witness accounts in an interview to Al Jazeera
We have three different reports from three different sources, and we would have to match them, one against the other in order to establish what is going on.
People easily confuse the different processes: the process of uranium enrichment and plutonium processing, and the light-water reactor which is built and works under completely different conditions.
North Koreans were promised two light-weight nuclear reactors back in 1994, which were never delivered. Now North Koreans are left without electricity, left without power and so they have to do something to compensate for
the loss of energy which was self-imposed. This is what they are trying to do right now.
They want to build several reactors at the same time, and the strange thing is that they try to tell different delegations, particularly US government delegations, different stories. The versions don't match up. And I don't think we need to believe these reports.
I think North Korea is simply bluffing ... trying to make the world believe that they are so sophisticated, and trying to make its domestic population believe that they will be rich, powerful by 2012 .. there is nothing to be worried about.
North Korea's rulers wants to attract attention to themselves. They want people to understand their state of desperation in terms of energy, electric power and nuclear power. They want to send a message to the world that something has to be done urgently.
As the North's economy suffers and the US and others tighten sanctions, unveiling the centrifuges could also be an attempt by North Korea to force a resumption of stalled international nuclear disarmament-for-aid talks.
The news of the centrifuges came as a high-level US envoy led a delegation to South Korea for consultations with regional leaders on North Korean issues.
The US state department said in a statement that Stephen Bosworth, the US special representative for North Korea, would arrive in Seoul on Sunday for talks with counterparts from South Korea, Japan and China.
The US team will later travel to Japan and China before returning to the US on November 24.
Days earlier a US research institute said a new nuclear reactor being built by North Korea at its Yongbyon complex could be used to produce weapons-grade plutonium.
The Institute for Science and International Security released satellite images on Thursday showing construction of an experimental light water reactor at the complex.
Hecker's claims were backed by Jack Pritchard, the president of the Korea Economic Institute, who said in Washington on Tuesday that he had visited the light-water reactor at the Yongbyon complex.
Pritchard told the New York Times on Saturday that he had heard the North boasting of another new facility, saying: "The intel agencies dropped the ball."
Barack Obama, the US president, recently warned that North Korea must show "seriousness of purpose" before six-party nuclear talks can resume, saying he was not interested in simply "going through the motions".
North Korea quit the aid-for-disarmament talks in April 2009 and staged its second atomic weapons test a month later. The talks group the two Koreas, the US, China, Russia and Japan.