North Korean leader Kim Jong Un guided the first test of a large new solid-fuel rocket engine at the country’s main spaceport on Thursday, according to state media, in a sign of progress on plans to build long-range nuclear missiles that can be launched more quickly in a conflict.

The Academy of Defense Science “successfully made the static firing test of a high-thrust solid-propellant motor with a thrust of 140tf (tons of force)” under Kim’s guidance, the Rodong Sinmun reported Friday, calling it “the first of its kind in the DPRK.”

The test took place at the Sohae Satellite