Satellite images released by a private, Washington-based group show that North Korea has made progress in the construction of a light-water reactor at its key nuclear Yongbyon complex north of the capital, Pyongyang.

The February 3 images of the nuclear site, released by the Institute of Science and International Security, show that the reactor's turbine building appeared externally complete — in contrast with September 20 images of the site that showed construction was still going on.

One analyst from ISIS says the images indicate the reactor's dome is not yet in place, meaning that the reactor is not operational.

The images were taken less than a month before North Korea agreed to suspend its testing of nuclear weapons and long-range ballistic missiles, as well as halt other nuclear activities, including uranium enrichment activities at Yongbyon in return for food aid.

The agreement followed February talks in Beijing between U.S. and North Korean officials, just two months after the death of North Korea's supreme leader, Kim Jong Il.

Stephen Bosworth, the former U.S. special representative for North Korea policy in the Obama administration, told VOA the deal could lead to progress in other areas, including an agreement on the relaunching of a deeper U.S. – North Korea dialogue and eventually the resumption of the six-party process.

American experts point out that after agreeing to shut down a plutonium nuclear reactor in 1994, Pyongyang went ahead with a secret uranium enrichment program, giving it another way to produce fuel for nuclear weapons. Many of these experts remain doubtful that North Korea will ever totally give up its nuclear weapons ambitions.