Kim Jong-un oversaw the ground test of an upgraded rocket engine, state media reported, marking another key step in its weapons programme.
Defence experts believe North Korea is planning to use its solid-fuel rocket engines for launching intercontinental ballistic missiles (ICBM).
The engines enable faster missile launches as they require little preparation before ignition.
The latest test was “part of the national defence development plan in the period of the new five-year plan”, Pyongyang’s official news agency said.
It was the first officially confirmed high-thrust solid-fuel engine test since September last year, when state media said an engine generated a maximum thrust of 1,971 kilonewtons.
The news agency reported the recent test had achieved a higher thrust of 2,500 kilonewtons.
The development demonstrates North Korea’s “resolve to acquire missiles capable of hitting targets around the globe”, Hong Min, an analyst at the Korea Institute for National Unification, said.
Kim said that North Korea’s defence capabilities had entered “a significant phase of change” in building up its strategic forces.
The North has already demonstrated it has mastered the engine technology needed to launch a missile capable of reaching the US with a lower-thrust engine, said Lee Ho-ryung of the Korea Institute for Defense Analyses.
The question is no longer whether a missile could reach the United States, but whether it could carry multiple warheads, she said.
A multi-warhead missile can strike multiple targets with a single launch while overwhelming defence systems through simultaneous, dispersed reentry vehicles.
“A multi-warhead missile needs higher thrust power because of its heavier weight,” she said. — AFP
