Recent satellite imagery suggests North Korea has been constructing a new ballistic missile submarine and may be preparing for testing, a U.S. think tank said Wednesday.

The images confirm photographs and reports published by North Korean media outlets in late July, in which leader Kim Jong Un was shown inspecting a newly built submarine at what is believed to be Sinpo South Shipyard, according to the Center for Strategic and International Studies.

“The construction and commissioning of a true (ballistic missile submarine) capability would represent a significant advancement of the North Korean ballistic missile and nuclear threat and complicate defense planning in the region,” the CSIS said.

Despite North Korean media reporting that the submarine’s “operational deployment is near at hand,” the Washington-based think tank analyzed the threat to be “emerging rather than imminent.” It projected that it could “easily take more than a year” before the new submarine would be fully operational, based on the time North Korea took to produce and deploy past submarines.

According to the center, satellite imagery of Sinpo South Shipyard taken since 2015 has provided circumstantial evidence indicating the shipyard is the home base of North Korea’s submarine building activities, and new infrastructure has been developed to support the deployment of a ballistic missile submarine.

In the images collected Monday, a support vessel was revealed to be moored alongside the test stand barge at the shipyard, together with a crane on the dock and people at the barge. Although the presence of the vessel “is interesting because in the past such vessels have been used to tow the barge out to sea for (submarine-launched ballistic missile) tests … there is no conclusive evidence that this will occur in the near future,” the center said.

The think tank also highlighted the presence of 15 cranes parked along the dock, known to be used at other North Korean navy bases and facilities to obscure submarine activities from overheard observation.

“These images suggest North Korea is making real progress in developing a second leg of the nuclear triad, bringing them closer to a survivable nuclear force and lessening prospects for full denuclearization,” the center said.

At a June meeting at the inter-Korean truce village of Panmunjom, U.S. President Donald Trump and Kim agreed that Washington and Pyongyang would resume stalled denuclearization talks within weeks, but they have yet to take place.