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

THE 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.

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. The reactor is nowhere near completion.

When fully operational, Yongbyon will be able to produce enough fissile material for one nuclear bomb a year, experts said.

NUCLEAR CAPABILITIES

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

NUCLEAR TESTING

Its first test in October 2006 produced a relatively low yield in its explosive force indicating problems with the North''s bomb design or plutonium at its core, experts said.

The May 25 test was stronger but experts believe it may only be about one-fifth to one-fourth as powerful as the plutonium bomb the U.S. dropped on the Japanese city of Nagasaki in 1945 at the end of World War Two.

NUCLEAR WEAPONS

Even though it has exploded nuclear devices, North Korea has not shown that it has a working nuclear bomb.

Experts said they do not believe the North has the ability to miniaturise an atomic weapon to place on a missile but the secretive state has been trying to develop such a warhead. It needs more nuclear testing to build one.

Even if it had, they say, North Korea does not appear to have the technology to guide the missile to a target.

North Korea''s ageing fleet of Soviet-era bomber would also have difficulty evading the technologically advanced air forces of regional powers the United States, South Korea and Japan to deliver a nuclear bomb outside the country.

URANIUM ENRICHMENT

The U.S. has long suspected that the North has a secret programme to enrich uranium for weapons, giving it another path toward an atomic bomb.

Such a programme can be conducted away from the prying eyes of U.S. spy satellites and the North can fuel it with the ample supplies of natural uranium it has in its territory.