North Korea seems to be on course to complete the construction of a new light-water reactor in its main nuclear complex in 2013, a U.S. think tank said Tuesday after analysis of satellite imagery.

A set of photos taken in May and June by commercial satellite shows cranes, a rectangular steel structure of considerable height and two metal beams, according to the Institute for Science and International Security (ISIS), based in Washington.

"New construction material has been placed on and near the reactor building," David Albright and Robert Avagyan with ISIS said in their report.

Although it has yet to be covered with the dome, they added, other major external work on the reactor appears to be "complete with most of the activity occurring inside the reactor building."

"The images were assessed for ISIS by a reactor expert. He estimated that the reactor could be completed in the second half of 2013," they said.

In May, the U.S.-Korea Institute at Johns Hopkins School of Advanced International Studies issued its own assessment of satellite imagery of the secretive nation's nuclear site in Yongbyon, about 60 miles north of Pyongyang.

It reported progress in North Korea's work on the new reactor, first revealed to the outside world in 2010.

But the institute said, "Overall, it may take another 1-2 years before the new facility becomes operational."

"Regardless of problems with its missiles and uncertainty about another nuclear test, the North is plowing ahead with this reactor, a key part of Pyongyang's strategy to expand its nuclear weapons arsenal," Joel Wit, a visiting fellow at the institute, wrote on his blog, 38 North, at that time. (Yonhap News)