The top U.S. envoy to North Korea said Monday that Pyongyang's claim that it has a large-scale enrichment facility that could produce weapons-grade uranium doesn't come as a surprise to Washington.
"We have been watching and analyzing the [North's] aspirations to produce enriched uranium for some time," Stephen Bosworth said Monday after a meeting Monday with South Korean Foreign Minister Kim Sung-hwan.
While the revelation is disappointing, Bosworth said, it does not represent a crisis.
Uranium enrichment potentially gives the North a second means of manufacturing nuclear bombs, in addition to its known plutonium-based program. At low levels, uranium can be used in power reactors, but at higher levels it can be used in nuclear weapons.
Asked about the possibility of resuming the stalled six-nation nuclear disarmament talks with the North, Bosworth said U.S. officials "do not at all rule out the possibility of further engagement with North Korea." But, he added, "I do not believe in engagement just for the sake of engagement or talking just for the sake of talking."
Bosworth's comments in Seoul came after a leading U.S. nuclear scientist was reportedly given a tour of the new facility, located at the Yongbyon complex — which the U.S. believes is the focus of Pyongyang's nuclear ambitions.
Siegfried Hecker, a Stanford University scientist and former director of the Los Alamos National Laboratory, said he visited Yongbyon, located just north of the capital, earlier this month and observed a highly sophisticated, industrial-scale enrichment operation. Hecker claimed to have seen hundreds of centrifuges used to enrich uranium, but the North says it has 2,000 of them.
North Korea told Hecker it began construction on the centrifuge facility in April 2009 and finished only a few days before the scientist's Nov. 12 visit.
The facility appeared to be primarily for civilian nuclear power, Hecker said. But he added that it "could be readily converted to produce highly enriched uranium bomb fuel."
Top U.S. military officials warned that the Yongbyon site could speed the North's ability to make and deliver viable nuclear weapons. It is not clear, however, why the country — which has kept a tight lid on its nuclear activities in the past — would reveal the facility.
South Korea's defense minister, Kim Tae-young, told lawmakers Monday that Seoul planned to discuss the possibility of having the U.S. bring tactical nuclear weapons back into the country in an apparent move to counter an escalating threat from the North.
Pyongyang has conducted several known nuclear weapons tests in recent years. The first, in 2006, is thought to have been largely unsuccessful, but a test three years later detonated a weapon about the size of the bombs that destroyed Hiroshima and Nagasaki in the closing days of World War II.
U.S. Secretary of Defense Robert Gates, speaking to reporters in Bolivia, said he believes that Pyongyang has nuclear weapons and that it can make more.
"An enrichment plan like this — assuming that’s what it is — obviously gives them the potential to create a number more," he said.
But Gates said that if the North Koreans' claim was true, they would have announced the facility's existence the United Nations. Even so, he echoed Bosworth's remarks, saying that uranium enrichment is fairly consistent with what he called "North Korea’s long-standing willingness to ignore U.N. resolutions and sanctions about its nuclear program."
Adm. Mike Mullen, chairman of the U.S. 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," 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."
The existence of a scaled-up enrichment facility would create a new set of worries for the Obama administration, which has shunned direct negotiations with North Korea following its nuclear and missile tests last year and in the wake of an international finding that a North Korean torpedo sank a South Korean warship in March, killing 46 sailors.
The United States has been working with China, Japan, Russia and South Korea since 2003 to persuade North Korea to abandon its nuclear programs.
"If what North Korea is claiming is really true, it's an extremely grave problem," Japanese Foreign Minister Seiji Maehara said at the outset of a meeting with Bosworth. "We must respond calmly and will step up our cooperation, particularly among Japan, the U.S. and South Korea."
With reporting from Mattia Cabitza in Santa Cruz, Bolivia, and NPR's Doualy Xaykaothao in Seoul, South Korea. This story also contains material from The Associated Press.