President Donald Trump has touted the missile defense system as a way to ward off threats from Russia, China and North Korea. Pyongyang sees offensive capability.

Trump on May 20 said he had picked a design for the Golden Dome system and named a leader of the ambitious $175 billion program.

Trump’s proposal, which as proposed remains years away from being operational, has many uncertainties, not least cost. The “Golden Dome,” modeled after Israel’s “Iron Dome,” would consist of a constellation of interceptors,