The US special envoy for North Korea on Monday said that pyongyang's claim of a secret new uranium enrichment facility is provocative and disappointing but not a crisis or a surprise.
Stephen Bosworth's comments, following a meeting with South Korean foreign minister Kim Sung-hwan, came as the United States and the North's neighbours scrambled to come to terms with pyongyang's revelation to a visiting American nuclear scientist of what has been described as 2,000 recently completed centrifuges.
"This is obviously a disappointing announcement. It is also another in a series of provocative moves'' by North Korea, Mr Bosworth said.
"That being said, this is not a crisis. we are not surprised by this. we have been watching and analysing the (North's) aspirations to produce enriched uranium for some time."
The American scientist, Siegfried Hecker, said in a report that he was taken during a recent trip to the North's main yongbyon atomic complex to a small, highly sophisticated, industrial-scale uranium enrichment facility.
Mr Hecker is a former director of the U.S. Los Alamos Nuclear Laboratory who is regularly given rare glimpses of the North's secretive nuclear program. he says the North Korean program had been built in secret and with remarkable speed.
It wasn't immediately clear why the North chose to reveal the previously hidden facility. It could be a ploy to win concessions in nuclear talks or an attempt to bolster leader Kim Jong Il's apparent heir. Regardless, it provides a new set of worries for the Obama administration, which has shunned direct negotiations with North Korea following its nuclear and missile tests last in 2009 in the wake of an international finding that a North Korean torpedo sank a South Korean warship in March, killing 46 sailors.
US Defence Secretary Robert Gates said he doesn't believe the facility is part of a peaceful nuclear energy program.
The facility could enable North Korea to build "a number" of nuclear devices beyond the handful it is presumed to have already assembled, Mr Gates said in Bolivia, where he is attending a regional defence conference.
Adm. Mike Mullen, chairman of the US Joint chiefs of staff, called North Korea "a very dangerous country."
"I've been worried about North Korea and its potential nuclear capability for a long time," Mr Mullen said on ABC's "This Week."
"This certainly gives that potential real life, very visible life that we all ought to be very, very focused on," he said.