The Defense Department's chief purchasing official Wednesday defended his attempt last month to give top Pentagon political appointees the power to veto searches of the private contractors who supply military equipment.

Robert Costello, undersecretary of defense for acquisition, told the House Armed Services Committee he wrote the memo after a contractor's office in St. Louis had been searched. Costello said he didn't object to the search but said it should not have been conducted without a prior review at the upper levels of the Pentagon."The system at that point had been short-circuited," Costello said. "The people at the local level had taken, perhaps, overly aggressive actions. If the system had been allowed to function as it was constructed to function . . . the access to the information could have been achieved without resort to the use of force."

The May 5 memo was written before the public ever learned of a two-year nationwide investigation into allegedly corrupt Pentagon contracting. The Associated Press obtained the memo Tuesday.

Rep. Les Aspin, D-Wis., chairman of the committee, told Costello that "the memo itself sends the wrong signal" to defense contractors. "The whole tenor of that (the memo) is awfully sympathetic to defense contractors."

Defense Secretary Frank Carlucci rejected the proposal, perceiving it as "interference in the conduct of criminal investigations," Air Force Col. David J. Shea, a Pentagon spokesman, said Tuesday.

The plan could have curtailed a crucial tool for investigators seeking evidence that top-secret Pentagon information was sold to private consultants, who then sold it to contractors. About three dozen searches have been conducted so far.

The Costello-to-Carlucci memo complained that Defense Department investigators had executed a search last February in a "sensational" manner by using some two dozen law enforcement officers and failing to give the company prior notice. That particular search was part of a fraud investigation, but was apparently unrelated to the nationwide probe.

Initially, Carlucci sent Costello a note saying, "This is a good idea," Shea said.

But Shea insisted the note referred only to Costello's suggestion that Pentagon investigators be trained to obtain evidence "in the least forceful and sensational manner."

Shea said Carlucci "doesn't want to be associated with" Costello's proposal that a "review and approval" system be established for search warrants.