It's a proposed system to detect, intercept and destroy missiles before they hit their targets. Radars are intended to detect the launch of hostile missiles. Then missiles are deployed to intercept them, either at the 'boost phase' soon after the hostile missile is launched or later in its flight. But President Bush says there are ''promising options for advanced sensors and interceptors'' for a boost-phase system, at least.
Experts differ substantially.
Groups such as the Heritage Foundation say missile defense is workable and necessary. It is highly unlikely that any candidate system can be shown to be militarily effective during the next eight years. He has given few details on how this would occur. Again, experts differ. No one knows for sure, but it won't be cheap.