A plan to move more than half of the Arlington County police department to temporary quarters has been killed because the owner of the property wants to lease the building to a high-tech firm, County Manager Larry J. Brown said yesterday.

"We're back to square one," Brown told the County Board yesterday about the county's search for a new home for 200 employes that the county wants to relocate to free up space in the back courthouse parking lot. Construction of the $150 million Court House Plaza high-rise complex is to begin on the lot next year.

Many people were looking forward to having a police operation in the neighborhood, said John Bernard, president of the nearby Ballston-Virginia Square Civic Association. "I guess, in a way, they let us down."

The property to be leased was across from Washington-Lee High School on North Quincy Street.

Most of those the county wants to move are members of the force's operations division, which includes the patrol car, motorcycle and tactical, or plainclothes, squads.

Brown said he does not expect the setback in the leasing arrangement, which was almost final, to delay construction of Court House Plaza. "It's just a matter of how cumbersome parking is going to be when the complex is started," he said.

Plans called for the county to spend about $200,000 renovating the building in an office complex in the 1400 block of North Quincy Street to meet police needs. They were to stay there for about three years until the county finds a permanent site for a new police station, now located behind the courthouse.

The move would have cost about $2.5 million over the life of the contract, Brown said.

The county will have to decide whether to put the money into another temporary site or into a planned new police station. No specific temporary sites are under consideration now, he said.

The county is, however, negotiating to use some land at Arlington Hall when the anticipated transfer of the 87-acre site from the Army to the State Department is completed.

The complex, now used for an Army intelligence and security command, is off Rte. 50 between Glebe Road and George Mason Drive.