(FOX NEWS) — President Donald Trump says Iran told him that the U.S. would have to dig out the “nuclear dust” at its facilities because it is buried so deep that Iran can’t get to it.

Trump told Fox News’ John Roberts that he doesn’t know at this moment how the U.S. would get into Iran to proceed with the removal, saying it is a matter for further negotiation.

Trump nevertheless emphasized that Iran cannot be allowed to ever get a nuclear weapon.