SEOUL: North Korea said Thursday that it had successfully conducted a high-powered, solid-fuel rocket engine test, which if confirmed would be a major step forward in boosting its missile attack capability against South Korea and the United States.

North Korea uses liquid propellants for its main ballistic missiles that target South Korea and US bases in the Asia-Pacific region. A long-range rocket that sent a satellite into orbit last month, whose militarized version can theoretically reach the US mainland, also uses liquid fuel.

Such missiles need to be fueled before they are launched, so it is relatively difficult to use them on short notice. The use of solid propellants, already loaded inside missiles, reduces launch preparation time and increases the mobility of the weapons, making it harder to detect signs before they are launched.

The North’s state media said that leader Kim Jong Un expressed delight after observing the successful testing of a “large-output solid fuel rocket engine,” which made an “earth-shaking” sound as it spit out a large beam of fire.

Kim said that the test will enhance a missile capability that will “mercilessly” strike enemies, an apparent reference to South Korea and the United States.

It is not possible to independently confirm the North’s statement or other high-profile announcements from the secretive, tightly controlled country.