North Korea on Thursday released new images of what it claims is its first nuclear-powered submarine, a massive vessel equal in size to some of the United States Navy’s attack subs.

Axar.az reports, citing CNN, the pictures released by state media showed leader Kim Jong Un inspecting the guided-missile submarine at an indoor construction facility, indicating it has not yet been launched.

Building a nuclear-powered submarine has been a long-held goal for Kim, who first discussed it at a ruling party congress in 2021, but the fact its rival, South Korea, has recently being given the blessing of the Trump administration to pursue its own nuclear-powered subs appears to have added urgency to Kim’s plans.

Such vessels come with many advantages. They can stay submerged for long periods of time – essentially for years, if they can carry enough provisions for the crew – whereas most conventionally powered subs must surface for air to run diesel engines, which in turn charge their batteries for running at depth.

They are also generally faster than conventionally powered subs and are in many cases quieter. Currently only the United States, Russia, China, France, the United Kingdom and India possess the technology.

State media said the vessel had a displacement of 8,700 tons, making it an equal to most of the nuclear-powered Virginia-class attack subs in the US fleet.

On Thursday, Kim again stressed its importance of the vessels to Pyongyang’s defense policy, which he said was “literally… based on the strongest offensive power,” according to a Korean Central News Agency (KCNA) report.

“We regard the super-powerful offensive capability as the best shield for national security in developing the armed forces,” KCNA reported Kim as saying.