FRESNO, Calif. — If elected, Sen. John McCain promised to award a $300 milliion prize to the automaker that develops a battery that “leapfrogs” commercially available plug-in hybrid or electric cars.

While campaigning in California, McCain proposed a federal standard to drive the conversion of flex-fuel technologies to allow more cars to run on alternative fuels, such as ethanol, in order to wean America off foreign oil. He also unveiled his Clean Car Challenge to reward the sales of zero-emissions vehicles.

“For every automaker who can sell a zero-emissions car, we will commit a $5,000 tax credit for each and every customer who buys that car,” McCain said. “For other vehicles, whatever type they may be, the lower the carbon emissions, the higher the tax credit.”

The announcement comes as automakers from around the world set goals of making their offerings more fuel efficient. Mazda, for instance, said Monday it planned to reduce fuel consumption of all of its vehicles sold globally by an average of 30 percent by 2015.

Also on Monday, General Motors signaled its intent of reducing its North American pickup and SUV product by some 170,000 units in the second half of this year. At the same time, GM will add 47,000 car and crossover units to meet consumer demand for smaller and more fuel-efficient cars while gas hovers above $4 per gallon.