North Korea said Wednesday it successfully tested new solid-fuel engines designed for intermediate-range ballistic missiles as it works on enhancing its nuclear-capable arsenal with more powerful, harder-to-detect weapons that can potentially target US military bases in Guam and Japan.

North Korea’s official Korean Central News Agency said the country’s military scientists tested the first-stage and second-stage missile engines on Saturday and Tuesday. The report did not say when the new missile system was expected to be completed.