Rather amusingly (if it wasn't so serious) President Putin has called Bush's bluff.

Since the missile defence system is to protect the West from rogue states like Iran, Putin has offered the option of a joint Russian/US project based in their leased based in Azerbaijan. This would be much closer to the trouble spots, and cover Europe well too. And guarantees no threat to Russia. Oh and undermines NATO and the allies who wanted the security.

Clever.