@ There are no significant defenses against cruise missiles. An enemy who finds his ballistic missile systems obsolete might build or buy cruise missiles. Shorter-ranged missiles could be launched from a cargo ship.
@ The system relies on satellites for launch detection and target tracking. This may simply encourage potential attackers to find a way to attack the satellites, perhaps with lasers.
@ The proposed missile bases in Alaska and North Dakota could not protect the US from missiles launched from the Southern Hemisphere. This might encourage a rogue nation to launch an attack from a ship at sea or from a temporary land base in the south.
@ China has announced plans to build enough missiles to overwhelm the US defense system. That larger arsenal is seriously threatening India and other Asian nations.--Stephen V Cole
WHAT ABOUT THE GAPS?: Critics of the pending US missile defense system have noted several flaws in the system design that have yet to be addressed: