North Korea has ordered U.N. inspectors to leave its Yongbyon complex, after saying it would quit international nuclear disarmament talks and restart the plant that makes bomb-grade plutonium.
Disabling the Soviet-era Yongbyon was a key plank in a disablement-for-aid deal the North reached with China, Japan, Russia, South Korea and the United States in 2007.
Pyongyang treats the nuclear research and production center as something of a trump card in international negotiations.
It last threatened to re-start the plant in September 2008, because it was angry at Washington for not taking it off its terrorism blacklist, and made minor but initial moves to re-start the plant, U.S. officials said.
Here are some facts about the complex located about 100 km (60 miles) north of Pyongyang:
The complex consists of a five-megawatt reactor, whose construction began in 1980, a fuel fabrication facility and a plutonium reprocessing plant, where weapons-grade material could be extracted from spent fuel rods.
The site also contains a 50-megawatt reactor whose construction was suspended under a 1994 nuclear deal with the United States. The reactor is nowhere near completion.
ESCALATION OF TENSION
In February 2005, North Korea declared for the first time that it had nuclear weapons. It conducted its first nuclear test with a plutonium-based device in October 2006.
DISABLEMENT OF YONGBYON
U.S. technicians began taking apart the three main working facilities at Yongbyon in November 2007, after a breakthrough February 2007 agreement.
North Korea said the toppling of the reactor's cooling tower in June 2008 was a demonstration of its commitment to the deal.
U.S. officials said the North has produced about 50 kg (110 lb) of plutonium, which proliferation experts said would be enough for six to eight nuclear weapons.
If North Korea re-starts Yongbyon, it could eventually extract enough material from spent fuel rods cooling at the plant to make one more nuclear bomb, adding to its meager stockpile of fissile material and making another nuclear test more likely.