Four of the Navy's most modern missiles, including several deployed with U.S. forces in the Persian Gulf, potentially suffer from manufacturing defects that can cause them to fail in combat, a draft report of the General Accounting Office has concluded.

The Navy purchased the missiles at a cost of several billion dollars over the last 16 months despite knowledge of the potential defects, according to the report obtained yesterday by The Washington Post.

The missiles listed were the Sparrow, Harpoon, Phoenix and HARM (high-speed antiradiation missile), which can be targeted at aircraft, ships and radar installations. Only the Phoenix had been widely reported to have defects.

The Navy sometimes ignored problems or waived requirements for the missiles, the report said. Instead of demanding repairs, the Navy obtained better warranties. In one instance, it bought hundreds of useless, partially completed missiles and put them into storage because a key part was defective and needed reworking.

Although the report does not refer to current operations in the Persian Gulf, the Sparrow failed twice when it was fired by F14 jet fighters at what was believed to be an Iranian plane over the Strait of Hormuz on Aug. 10.

Since mid-1986 the Navy has "accepted hundreds of the {Sparrows} that were suspected of having defects that could affect missile performance," the report said. The defects included improper wiring, poor soldering, inadequate detonators, and wings that cannot be properly folded before stuffing the missile into its launcher tubes.

Navy officials said yesterday that none of the problems has affected the operation of the Sparrow, which they said has been more reliable than expected. But the GAO reported that the Navy has been sharply at odds with one of the principal Sparrow manufacturers, the Raytheon Corp., over the cost of repairing missiles that failed routine tests.

The Sparrow costs an average of $183,000 each, the GAO said.

Similar defects were found last year in soldering for the HARM, designed to be fired by A7, F18 and EA6B carrier-based aircraft at enemy radar installations.

Discovery of the defects caused the Navy to relax the soldering specifications, wiping out the findings for all but a few of the defects in the $303,000 missiles, the GAO said. This decision provoked protests among personnel at the Defense Logistics Agency and the Naval Weapons Center in China Lake, Calif., because of "the message the revisions may send to the contractor concerning inspection and overall quality control," according to the GAO report.

The report also said the Federal Bureau of Investigation is checking allegations that a HARM subcontractor, the Genisco Technology Corp., had falsified test data on the component that activates the missile's "target seeking device." It said as many as 1,300 purchased missiles were affected, although preliminary tests indicate the problem is not serious.

Potentially more serious defects have been identified in the Harpoon, an $854,000 missile fired at ships from aircraft, submarines and surface vessels, the GAO said. In particular, it said a "soldering problem in a critical component, the altimeter, could lead to missile reliability problems after several years of deployment."

The GAO said the altimeter, which helps guide the missile to its target, might be particularly prone to failure "in a fleet environment where there can be considerable heat and humidity."

On the Phoenix, the report suggested the Navy had botched its management of the $922,000 missile, currently being produced by the Hughes Aircraft Corp. and stored in a Tucson warehouse. None of the missiles can be deployed until defects are corrected in the component that arms and ignites the missile.