The Reagan administration yesterday tried to end the long debate over air bags in cars by announcing that unless states pass laws to make motorists wear seat belts, the federal government will require some sort of automatic crash protection system.

Transportation Secretary Elizabeth Hanford Dole said the government would require car manufacturers to start equipping some cars with passive restraints by 1986, but will suspend that rule if states with two-thirds of the U.S. population enact mandatory seat belt use laws.

Dole's decision effectively reverses previous Reagan administration efforts to reduce auto industry regulation and throw out passive restraint requirements drafted in 1977 by the Carter administration. The Carter regulation would have required air bags or automatically closing seat belts in all new cars by September 1983.

Dole said the decision would save lives immediately by encouraging seat belt use. But highway safety advocates claimed the ruling would mean the death of air bags, and the insurance industry and auto importers both immediately went to court to challenge Dole's decision.

Joan Claybrook, who headed the National Highway and Traffic Safety Administration under President Carter, said Dole's rule "excuses manufacturers of all responsibility to make safer cars."

Claybrook and other critics who wanted mandatory air bags contended that auto makers would substitute cheaper and less effective safety devices and would stall in the hope that states will make all passive restraints unnecessary.

Under the rule announced by Dole, auto makers must start equipping 10 percent of their new passenger cars with devices such as inflatable air bags or automatically closing seat belts by September 1986.

A phase-in schedule calls for passive crash protection in 25 percent of all new cars by September 1987, 40 percent of new cars by September 1988 and all cars by 1989 for the 1990 model year.

The Supreme Court last year ruled that the NHTSA under President Reagan had not adequately justified its rejection of the Carter air bag rule. The court ordered the agency to let the rule stand, come up with a better reason for killing it or replace it with a new regulation.

Dole's solution would change the original proposal by giving car manufacturers the option of substituting "new technologies" for air bags or passive seat belts. General Motors Corp. says it can meet federal crash standards in some models with structural innovations such as crushable hoods, more heavily padded dash boards and collapsible steering wheels.

And the administration plan would mean no passive restraints of any kind would be required if states adopt mandatory seat belt laws.

Dole said DOT will lobby hard for state seat belt laws. The department will pay for half of a $40 million-a-year educational program to encourage drivers to buckle up and to urge passage of seat belt laws. The New York state legislature recently passed the first such law in the nation and Gov. Mario Cuomo is expected to announce today whether he will sign it.

Dole said the administration would give auto makers an incentive to use air bags or "friendly interiors" by counting each car equipped with them as 1 1/2 cars toward the annual quota. Cars with automatic seat belts would count as one.

Steering a tricky course through White House opposition to regulation and political pressures for a stricter auto safety standards, Dole said her decision was based solely on "the public interest" and "will save as many lives as possible, as soon as possible."

She said she hoped that the campaign for seat belt laws would lead to greater public demand and "market incentives" for systems that protect drivers and passengers despite a reluctance to buckle up.

Only 12 percent of U.S. drivers use their belts voluntarily, DOT says. There were 37,800 fatal crashes last year, and fewer than 2 percent of the victims were wearing seat belts, the department reports.

A Gallup poll published Sunday showed 65 percent of those surveyed opposed a $50 penalty for not wearing a seat belt.

Following Dole's announcement, State Farm Mutual Automobile Insurance Co. and the National Association of Independent Insurers filed suit in the District of Columbia Circuit Court of Appeals, challenging Dole's authority to make a federal standard contingent on state action, and asking for speedier installation of automatic protection systems.

Later in the day, the Automobile Importers of America Inc. filed suit in federal court in San Francisco challenging Dole's decision.

Claybrook, now president of the consumer group Public Citizen, said auto makers will opt against air bags and "put in cheaper systems" because they "won't want to invest in a technology that might be worthless" if enough states pass seat belt laws. She said air bags would save 9,000 lives a year and prevent 65,000 crippling injuries over the next 10 years, she said.

The car manufacturers have argued that air bags are too costly and are not effective without a lap belt anyway. Mercedes-Benz of North America, the only company in America to offer air bags as an option, prices them at $880 for one on the driver's side only.

General Motors Corp. and Ford Motor Co., which both support mandatory seat belt laws, said they were pleased with the rule. Seat belt laws "will start saving lives immediately," said John Hartnett, a GM spokesman.