North Korea is advertising what some American scientists are calling a stunning advance in its nuclear program.
Robert Carlin and two other Stanford University nuclear experts were recently invited to North Korea's Yongbyon nuclear facility, and what they saw there rocked them on their heels.
"It's going to drop like a bombshell," Carlin said. "We walked over to the window and we were suddenly surprised to see row after row after row of centrifuges. The North Koreans say it was 2,000. It was a lot."
Those nuclear centrifuges were designed to enrich uranium. In an exclusive interview with ABC News, Carlin said the facility is vastly more advanced than he or any nuclear expert who's spoken publicly expected.
"None of the experts that I knew predicted the North Koreans could build anything like this number. ... Everybody predicted they were at a very early stage," Carlin said. "I'm not kidding you, I think our minds went blank for a second because it was so stunning."
North Korea insists the site is designed only for nuclear power, but American experts fear the Yongbyon facility could quickly be converted to make highly enriched uranium for nuclear weapons, or worse, North Korea might be hiding another site that is already doing just that.
"It alarmed me and the reason was it was such a surprise. It showed me that the policy that we've been following seems to be at a dead end," Carlin said.
That policy -- sanctions -- clearly did not bar North Korea from obtaining the technology it needed.
North Korean premier Kim Jong Il might be hoping to bargain with the United States and other nations, hoping they'll buy off the impoverished country's nuclear technology.
"One motive might be that North Korea likes to use provocation as a way to coerce the United States and the world into negotiations and even into giving things that they want, including food, fuel and recognition by the outside world," said Victor Cha, director of Asian Studies at Georgetown University.
Carlin and his team flew home and informed the White House, which rushed to send an envoy to Asia to consult with allies.
Diplomats and scientists alike largely agree that the latest developments -- in the words of Carlin -- are a game-changer. A military attack is unthinkable, but so is allowing a runaway nuclear program.
In a report on the meeting, Carlin's colleague Siegfried Hecker concludes: "The only hope appears to be engagement."
That means restarting stalled negotiations with North Korean leaders, whose hand appears to have been dramatically strengthened.