Implementing the "Brilliant Pebbles" space-based defense plan could reduce the $69.1 billion price tag attached to the early development stage of Star Wars research, says a Pentagon official.

Lt. Gen. George L. Monahan Jr., director of the Strategic Defense Initiative, told members of the Senate Appropriations defense subcommittee Thursday that Brilliant Pebbles could trim the cost of Phase I of Star Wars. He did not provide specifics.The United States has invested about $17 billion in SDI, commonly known as Star Wars, and members of the Senate panel expressed reservations about the direction and the high price of the research program.

"The members of Congress and their constituents must ask themselves whether the nation can afford SDI and whether the return on the investment is justified," said Sen. Daniel Inouye, D-Hawaii, chairman of the subcommittee.

Inouye called current spending on Star Wars "robust," and said the $17 billion "could have been funded in other weapons."

Sen. Tom Harkin, D-Iowa, criticized the research program as "ill-defined with conflicting goals."

"Ronald Reagan told us SDI is to protect people. It looks like we're going to protect missiles," Harkin said.

But Monahan sought to assure the lawmakers as he described the Brilliant Pebbles process and the Pentagon's current plans.

Monahan said the Defense Science Board and the Jasons, a group of university professors, mostly physicists, will review the concept for the department this summer.

"This fall, subsequent to Brilliant Pebbles study efforts . . . we will re-examine our space-based architecture with a view toward the degree of incorporation of this concept," Monahan said.

Under the system, 3,000 to 5,000 satellites, about three feet long and weighing less than 100 pounds each, would be placed in orbit about 400 miles above the Earth.

Brilliant Pebbles is supported by outgoing SDI chief, Lt. Gen. James Abrahamson, who predicted in a Feb. 9 memorandum that it could be deployed in space for about $25 billion, far less than the estimates of $45 billion for other SDI orbital systems.

Monahan said recent budget cuts have forced the Pentagon to delay work on some Star Wars research, including a six-month slip in development of a tracking satellite.