The Bush administration is revising its "Star Wars" plan in order to build a defense against limited strikes from enemy missiles instead of an all-out attack by the Soviet Union, the project's director says.

The change reflects the administration's view that improved U.S.-Soviet relations and the collapse of communism make it less likely that Moscow would unleash its arsenal of thousands of globe-circling nuclear ballistic missiles.It also points to a decline in congressional support for spending billions of dollars a year on the Strategic Defense Initiative, commonly called Star Wars, and the administration's desire to deploy some form of missile defense system in the mid-1990s.

The new system, not yet officially announced, is being designed to defend against "tens or hundreds" of missiles fired accidentally by the Soviets or deliberately by a Third World renegade leader, rather than the thousands of missiles that would be expected to fill the skies in a full-scale strike by Moscow.

Henry F. Cooper, the Pentagon official in charge of the Strategic Defense Initiative, said in an interview Thursday that the revised anti-missile system could be deployed more quickly than the system originally envisioned.

He said he could not give a target date for deployment or a precise estimate of the cost.

"I would say it's still somewhat uncertain but obviously less than" the Pentagon's estimate of $55 billion for the initial phase of the current Star Wars plan.

About $20 billion has been spent on Star Wars research since 1984.