The Reagan administration will begin a new review of passive restraint regulations by Oct. 15 and will decide within a year whether to require the use of air bags or automatically closing seat belts, officials said yesterday.

The announcement at a Senate subcommittee hearing was the administration's first detailed response to a Supreme Court ruling in June that overturned its attempts to scrap passive restraint rules.

Proposed rules requiring new cars to be equipped with air bags or automatic seat belts beginning with the 1982 model year were withdrawn by the National Highway Traffic Safety Administration in 1981 largely because of opposition from domestic automakers.

But the Supreme Court ruled on June 24 that NHTSA failed to provide adequate reasons for dumping the rules and ordered the agency to review the matter.

The decision left the administration with the choice of finding better reasons for killing the rules or of coming up with new rules altogether.

There was government and media speculation that the administration would choose the first option and draft a new death sentence for the rules. But Deputy NHTSA Administrator Diane K. Steed and Christopher DeMuth, administrator for regulatory affairs in the Office of Management and Budget, said yesterday such speculation was groundless.

"We are convinced that the passive restraints technology works," Steed told Sen. John C. Danforth (R-Mo.), chairman of the surface transportation subcommittee. "We do not intend to rescind the rule."

"There is no substance whatsover" to reports that the administration has already decided how it will respond to the court, Demuth said. He said allegations from consumer advocates and others that OMB is giving NHTSA or the Department of Transportation marching orders in the passive restraints case "are absolutely wrong."

Danforth indicated he was not convinced. "I believe there is a philosophical opposition on the part of the administration to safety regulation," the senator said. He accused the administration of deliberately delaying reinstatement of the rules.

"The unfortunate result of it is that people are dying. I've given up on the administration. I think we're going nowhere," he said.