The test likely indicates Kim is intent on enlarging and modernizing an arsenal of missiles capable of reaching the United States mainland.
The report on Sunday from Korean Central News Agency came days after Kim delivered a speech at North Korea's Parliament pledging to irreversibly cement his country's status as a nuclear power and accusing the U.S. of global "state terrorism and aggression," in an apparent reference to the war in the Middle East.
Kim watched the ground jet test of the newly upgraded engine using a composite carbon fiber material, according to KCNA, which reported the engine's maximum trust is 2,500 kilotons, up from about 1,971 kilotons reported in a similar solid fuel engine test in September.
A push to increase the engine power is likely associated with efforts to place multiple warheads on a single missile to increase chances of defeating U.S. defenses, observers say.
KCNA did not report exactly when or where the test occurred.
