North Korea said Kim Jong Un watched a ground test of an upgraded solid-fuel engine for weapons capable of reaching the U.S. mainland, according to state media reports Sunday.
The Korean Central News Agency said the test involved a solid-fuel engine using a composite carbon fiber material. KCNA also reported that Kim observed the ground jet test, and it presented the engine upgrade as part of a broader effort to improve North Korea’s “strategic strike means,” a term used for nuclear-capable ballistic missiles and other weapons.
KCNA said the new engine’s maximum thrust was 2,500 kilonewtons, compared with about 1,970 kilonewtons that North Korea had reported for a similar solid-fuel engine test in September. The KCNA report did not specify when or where the test occurred.
AP also reported that North Korea portrayed the engine test as a significant development that would boost its strategic military arsenal. The report said Kim’s stated goal involved obtaining more agile, hard-to-detect missiles targeting the U.S. and its allies, which officials said solid-fuel technology can support.
Some external analysts said the North’s portrayal may not fully match the underlying engineering picture. Lee Choon Geun, an honorary research fellow at South Korea’s Science and Technology Policy Institute, said the North Korea report could be “bluffing” because it did not disclose some key information, such as the engine’s total combustion time.
Observers noted that North Korea’s earlier accounts around similar engines had drawn skepticism from outside experts. In 2024, North Korea claimed to have successfully test-launched a multiwarhead missile, and South Korea quickly dismissed it as deception to cover up a failed launch.
In the technical debate around the latest report, experts said solid-fuel designs can be easier to move and conceal than liquid-fuel systems, which generally require fueling before liftoff and cannot last long. That characteristic, analysts said, increases the operational value of solid-fuel engines as North Korea seeks capabilities for long-range strikes.
The reported engine-thrust increase also raised questions about how quickly North Korea could turn ground-testing progress into a functioning intercontinental ballistic missile. Observers said North Korea has tested ICBM-capable systems in recent years that showed potential range to reach the U.S. mainland, including solid-fuel ones, but some foreign experts have pointed to technological hurdles such as whether warheads can survive atmospheric reentry conditions.
Lee said the solid-fuel engine program may face delays or reflect a decision to develop a better engine, with possible Russian assistance discussed as one factor. He said cooperation between Russia and North Korea has deepened in recent years, including reports that the North sent troops and conventional weapons to support Russia’s war against Ukraine.
As North Korea continues its arms build-up, the reports also tied the latest tests to the state’s broader nuclear posture, saying the effort has accelerated since high-stakes diplomacy between Kim and U.S. President Donald Trump collapsed in 2019. In February, Kim’s ruling Workers’ Party congress left open the door for dialogue with Trump but urged Washington to drop demands for North Korea’s nuclear disarmament as a precondition for talks.