Forget the missile defense system. I say listen to Newt:
“In the immediate and present danger, the United States should not wait to attempt to shoot the missile down after it is launched. There is no proven reliable technology and no evidence that we could succeed. Instead, we should destroy the missile on its site before it is launched. Our ability to preempt the launch is nearly certain.”
Failing that, a post over at Blackfive points out that it is a lot easier to swat the thing out of the sky on it’s ascent than it’s descent.