Auto makers and federal officials made conflicting claims yesterday over the safety of air bags as Congress began considering whether to overrule an administration decision to require new safety devices in cars.

Transportation Secretary Brock Adams argued for his plan to require either air bags or automatic safety belts. "We have too long ignored a lifesaving system of techical merit and proven potential," he said.

This view was disputed by executives of the Big Four auto makers, who told a Senate Commerce Subcommittee the devices have not been proven effective. The auto makers urged delay of the Adams proposal for more tests, primarily on air bags.

Congress has until early October to pass a resolution keeping the Adams plan from becoming law. Resolutions have been introduced in each chamber and the House opens hearings on the issue today.

Under the proposal made June 30 by Adams, auto makers would be required to build the safety systems into large cars beginning with 1982 models and all cars by 1984.

In addition to air bags, the proposal would allow seat belts that wrap around passengers automatically without having to be buckled by passengers.

Ford Motor Co. vice president Herbert Misch told the subcommittee that his company will launch a "substantial test program" involving passive restraint safety systems on some 1980 and 1981 model cars.

Misch disclosed that Ford plans to offer the air bags or passive belts prior to the new federal requirement.

If engineering plans are successful, the passive belts will be offered as an option on at least one mid-sized car line in the 1980 model year, he said.

In the 1981 model year, air bags will be optional on at least one full-sized line, and Ford plans to offer the passive belts as an option on a 1981 subcompact car.