In a 120-page report on North Korea's quest of weapons of mass destruction, the International Institute for Strategic Studies (IISS) said it was "impossible" to reach a firm conclusion about Pyongyang's nuclear capability.

"On the one hand, a plausible case can be made that North Korea has enough plutonium for a very small number of nuclear weapons," it said in the report, titled "North Korea's Weapons Programmes: A Net Assessment".

But on the other hand, the IISS said it could not confirm how much plutonium North Korea actually has, and whether it can build "a deliverable nuclear weapon" from it.

"From a public policy standpoint, and given the stakes involved, the case is strong enough that it would be imprudent to conclude that North Korea does not have nuclear weapons," it said.

The United States believes North Korea already has one or two crude nuclear bombs and could speedily build more using a stockpile of spent nuclear fuel at its Yongbyon nuclear complex north of Pyongyang.

North Korea says it has already reprocessed the rods, yielding enough plutonium for five or six bombs.

The IISS report also concluded that North Korea's secretive communist regime "probably" has developed chemical weapons, although there is little authoritative information as to their type or quantity.

WAR.WIRE