Pentagon officials clashed with two Republican senators yesterday, testifying that they do not believe contractors should have to guarantee the weapons they produce.

Mary Ann Gilleece, deputy undersecretary of defense for acquisition management, said requiring warranties would shift the risk to contractors, but contractors would then shift "exorbitant costs" back to the government.

Congress is trying to reform the weapons procurement process in the wake of reports of shoddy performance or inadequate testing. Many of the proposals for change have come from Republican senators, such as William V. Roth (Del.), Ted Stevens (Alaska) and Mark Andrews (N.D.), who say they support defense spending but believe the Pentagon may not be spending wisely.

Gilleece and other Defense officials told the Senate Appropriations subcommittee on defense that the Pentagon protects itself more thoroughly with its own testing and quality assurance programs than it would with required warranties. That contention contrasted to recent complaints from top officials, including Army Chief of Staff Gen. John A. Wickham Jr. and Deputy Secretary Paul Thayer, about shoddy workmanship in weapon production.

"When I buy a tractor, it costs six figures, and my banker insists I get a warranty because of its cost," Andrews said. "Then why can't we get an Allison transmission in a tank with a similar warranty?"

Gilleece responded that the Pentagon frequently buys untested, state-of-the-art technology that cannot be warrantied like a conventional car, tractor or jet. She said military officials need the freedom to change specifications and requirements as a weapon is developed.

Sen. Warren B. Rudman (R-N.H.) said he agreed that warranties cannot be required for innovative weapons, but he questioned why they could not be mandated once a system goes into regular production. Dina Rasor, director of the private Project on Military Procurement, said many similar or identical aircraft and vehicles carry substantial warranties when sold to civilians.

Gilleece said the Pentagon does, in fact, buy many of its commercial products with warranties, and said about one-third of the 4.1 million items in its inventory are covered in some way. But she said she did not know what proportion of the money the Pentagon spends goes to warrantied items, and other Pentagon officials said that figure is substantially below one-third.