California ? California air regulators on Thursday gutted rules seeking to place tens of thousands of zero-emission vehicles on the road, instead ordering automakers to produce a fleet of cleaner-burning hybrids.

The decision is expected to affect 12 other states that had adopted California’s target for zero-emission vehicles, defined as those powered solely by batteries or hydrogen fuel cells.

The California Air Resources Board voted to lower by 70 percent the number of those vehicles that automakers must sell here and in the states that intended to follow California’s get-tough rules for vehicle emissions.

Instead, the air board said the six largest automakers must sell nearly 60,000 plug-in hybrid vehicles in California while they develop the more advanced technology that will allow mass production of pure zero-emission vehicles.

Board chairwoman Mary Nichols described the move as a major step toward putting cleaner cars on the road. The plug-in hybrids envisioned by the air board have yet to be produced but are in development by several automakers.

“We’re introducing a whole new category of vehicles to the public,” Nichols said. “I don’t think it’s a step backwards in the real world.”