Remember, if it's a big rock, fixin to hit some big city: ya gotta take it out, but if it's a missile(s). let er come on in. Show em we're peaceful. (And stupid.)
I recently read a Sci-fi story about a combatant in a war that had hollowed out and asteroid and hid a command and control center with nuclear missiles in side. Their enemies never suspected, until it was too late..........