A limited version of the "Star Wars" missile defense system that would protect against short-range attacks could be ready in five years at a cost of $9 billion, according to senior defense officials.

Henry Cooper, director of the Pentagon's Strategic Defense Initiative Office, told reporters Tuesday that the modified program would use ground-based missile interceptors that would destroy their targets in various stages of flight.The missile defense system, called G-PALS, or Global Protection Against Limited Strikes, would use a satellite tracking system for guidance, he said.

In a new twist, Cooper said his office also is considering adapting the anti-missile system for use aboard ships and aircraft to defend against short-range attacks.

Cooper said a more elaborate system designed to intercept long-range ballistic missiles could be deployed by the end of the decade at an additional cost of about $32 billion.

Congress cut the Pentagon's anti-missile budget for this fiscal year to $2.89 billion, far below what the Bush administration had requested. Cooper said that unless Congress provides additional money in future years, the G-PALS system would not be operational until the 21st century.

Last month, President Bush ordered that the "Star Wars" program, which originated in the Reagan administration, be refocused to concentrate on a defense against accidental or unauthorized launches of a couple of hundred long-range missiles, rather than a full-scale attack.

A companion effort, known as theater missile defense, would provide a similar level of protection against short-range missiles.