One such expert, former National Nuclear Security Administration acting principal deputy administrator Corey Hinderstein, said even a simple test consisting of setting off one warhead in an underground shaft could cost upwards of $100 million.

Russia said it tested a nuclear-powered cruise missile and torpedo, two of its experimental weapons, in recent days.

The Poseidon’s power significantly exceeds the power of even our most promising Sarmat intercontinental range missile,” Putin said.

President Donald Trump announced he is ordering the U.S. to resume nuclear testing, leaving experts wondering what this would entail and how it would be implemented.