North Korea may finish work by late 2013 on a light-water reactor that could be used to support its nuclear weapons program, a US think tank said Tuesday.

The Institute for Science and International Security published satellite images taken in May and June of the Yongbyon nuclear complex showing cranes and metal beams that could be used to bring heavy components into the reactor.

An expert who reviewed the photographs "estimated that the reactor could be completed in the second half of 2013," the Washington-based think tank said in a report.

Most major external work appears to be complete except for covering the reactor with a dome, which has been seen lying next to the site since November, the think tank said.

A separate assessment of earlier satellite imagery, released in May by Johns Hopkins University's US-Korea Institute, also described advances but doubted the facility would be operational before 2014 or 2015.

North Korea first disclosed in 2010 to visiting US scientists that it was working on a new light-water reactor, ostensibly for civilian purposes. The impoverished nation desperately needs energy, but the reactor could also be run to produce weapons-grade plutonium.

The reclusive regime has based its nuclear weapons program on plutonium and has tested two nuclear bombs since 2006, triggering repeated international crises.

Pyongyang has also said that it is building a uranium enrichment plant to produce low-enriched fuel for the new reactor. Scientists believe the accompanying site could be converted to produce highly enriched uranium, giving North Korea a second way to make nuclear weapons.

Young leader Kim Jong-Un's regime said it would suspend nuclear and missile tests along with uranium enrichment under a February 29 deal with the United States in return for badly needed food assistance.

But the agreement quickly collapsed after North Korea launched a rocket on April 13 in what US officials believe was a disguised, albeit unsuccessful, missile test.