A well-known international research group says intelligence agencies believe North Korea has developed and deployed nuclear warheads theoretically capable of being placed on missiles.  The assessment, to be explained in more detail in a report due out this week, is certain to fuel concerns about the North's planned long-range rocket launch this month.  

Daniel Pinkston, a Seoul-based analyst for the International Crisis Group, says North Korea appears to have made an alarming advance in its nuclear weapons program.

"Information I've obtained seems to indicate that they [North Korea] have assembled nuclear warheads for the Rodong and that there are two storage facilities for them in the Northern part of the country," Pinkston said.        

The "Rodong" is a North Korean medium-range missile that can reach all of South Korea and most of Japan.  North Korea conducted an underground nuclear weapons test in 2006, but experts have doubted whether the North would be able to produce a nuclear bomb small and light enough to mount on a missile.

In a report due out this week, Pinkston says there is a growing consensus within international intelligence agencies that Pyongyang has already produced several such warheads and might be able to deploy them in short order.

"The assessment is that they probably store the fissile material and the other components separately, so that they wouldn't have a nuclear accident - it wouldn't detonate accidentally.  And it would take a day or two - probably two days - to assemble those and get them ready, and to transfer them to the military, transfer them to the missile units for launch," Pinkston said.

The warning is likely to increase even further the level of international concern over North Korea's planned launch of a long-range rocket, early next month.  If weather is favorable, liftoff is expected to happen as early as this coming Saturday.

Pyongyang says the rocket will be carrying what it calls a "communications satellite" on a legitimate space research mission.  South Korea, the United States, Japan and the European Union says the launch will violate a United Nations resolution imposed after the North's nuclear test.

Pinkston does not specify which nations the information comes from - but Japan, South Korea, and the United States have all warned for years the North seeks to produce nuclear-tipped missiles as soon as it can.  He says, even with the best intelligence, there is room for doubt.

"Even if you went directly, and you were given a private tour by Kim Jong Il and his staff, and you were taken to an underground facility and shown what appeared to be a nuclear warhead, it could still be a hoax.  So, until you actually see it, there can be no absolute certainty," he said.

Pinkston's summary of international intelligence data is due out this week, in a new report by the International Crisis Group.