New York yesterday became the first state to require motorists to wear seat belts, as the Reagan administration and auto safety advocates debated over whether other states should follow.

New York Gov. Mario Cuomo signed into law a bill that requires all front-seat auto occupants to wear seat belts or face a $50 fine. The law takes effect Jan. 1, 1985.

Transportation Secretary Elizabeth Hanford Dole ruled Wednesday that the auto industry would have to begin equipping cars with air bags or automatically closing seat belts by the 1987-model year unless states representing two-thirds of the population pass seat belt laws.

Although the auto makers would have to begin equipping cars with new crash protection systems by the 1987-model year, the deadline for the new state laws is not until April 1, 1989.

Dole said mandatory seat belt laws would be the quickest way to save the most lives, and that the Department of Transportation would spend $20 million a year to urge passage of such laws.

But some state lawmakers are complaining that the Reagan administration is forcing them to choose between seat belt usage laws and automatic crash protection systems.

Cuomo criticized the Dole rule after signing the seat belt law yesterday. "To the extent that it's air bags or laws, I don't like that at all. I'm sorry she's using what we did as a possible excuse for not requiring passive restraints ."

New York's seat belt law sponsor, Republican state Sen. Norman Levy, said yesterday he will soon introduce a proposal to require air bags in 1987-model cars operating in New York.

Connecticut state Rep. Christine Niedermeir, who supports air bag requirements, said yesterday that she had planned to introduce a seat belt law in her state, but now is not sure that she should. Dole's decision "places states in a serious dilemma," Niedermeir said. "Do we risk the short-term safety of our citizens in order to rely upon the eventual added protection of air bags, or do we adopt seat belt legislation today and forego the advantages of air bags and other automatic occupant restraints?"

Some states may "sit on their hands and wait for air bags," said Niedermeir, who chairs the transportation committee of the National Conference of State Legislatures.

New Jersey state Sen. Walter Rand said he expects a seat belt law to be introduced in that state soon and predicted it would pass, but he expressed reservations about it. "Maybe we'd be defeating the very thing we want to get," he said, referring to automatic protection requirements. "Maybe we should wait and force the feds to do what they should."

The NCSL said 20 states have introduced seat belt legislation this year, but the proposals have already died in 13 states, including Illinois, Texas, Minnesota and Rhode Island.

In addition to the $50 fine on front seat occupants, the newly passed New York law requires that children under 10 years old wear belts or be fastened in safety seats in the back seat. Out-of-state residents driving through New York must comply as well.

Rand doubted whether seat belt laws could be enforced, and other critics of Dole's rule point to strong public opposition to seat belt laws. A Gallup poll published Sunday said 65 percent of those surveyed opposed a seat belt law such as New York's.

The poll also showed that support for seat belt laws had increased 11 percent since 1982, and Dole said the trend will continue.

Dole also said the swift passage of mandatory child restraint laws showed public support for auto safety laws. In January 1981 only two states required safety seats for small children. Only Texas and Wyoming now lack such laws.

The campaign to pass seat belt laws will raise public awareness and create greater public demand and "market incentives" for air bags, passive seat belts and other automatic protection devices, Dole said.

Auto makers strongly supported Dole's call for seat belt laws, arguing that air bags are too costly for most car buyers. Mercedez-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.

Niedermeir said she expects to see the auto industry lobby hard for passage of seat belt laws, concentrating primarily on the large industrial states.