FACTBOX - A look at North Korea's nuclear arms ambitions

SEOUL (Reuters) - North Korea's Foreign Ministry called on Monday for direct talks with its long-time foe, the United States, and said it was ready to return to stalled six-way nuclear disarmament negotiations.

The following is a look at destitute North Korea's decades-long pursuit of nuclear arms:

YONGBYON FACILITIES

The Yongbyon complex is at the heart of the North's plutonium weapons programme. It consists of a five-megawatt reactor, whose construction began in 1980, a fuel fabrication facility and a plutonium reprocessing plant, where weapons-grade material is extracted from spent fuel rods.

Under an earlier agreement, North Korea began to close down the facility, but this year announced that in the face of U.S. hostility it would restore parts of the plant.

The site, about 100 km (60 miles) north of Pyongyang, also contains a 50-megawatt reactor whose construction was suspended under a 1994 nuclear deal with the United States. That reactor is nowhere near completion.

When fully operational, Yongbyon can produce enough plutonium for one nuclear bomb a year, experts say.

NUCLEAR CAPABILITIES

U.S. officials said prior to the North's May 25 second nuclear test it had produced about 50 kg (110 lb) of plutonium, which proliferation experts say would be enough for six to eight nuclear weapons. It could eventually extract enough material from spent fuel rods is says it is reprocessing at Yongbyon to make one more bomb.