The executives and lawmakers also discussed ways for government to help struggling Detroit carmakers better compete with overseas rivals like Japan's Toyota Motor Corp. and Honda Motor Co.

Toyota and Honda have gained market share with cars that go farther on a gallon of gas and new gas-electric hybrids, while GM, Ford and Chrysler have slumped with their marquee pickups and sport utilities that are less fuel efficient.

Ford, GM and Chrysler have increased production of alternative or flexible fueled vehicles to retain buyers and attract new ones concerned about high gas prices and the impact of fossil fuels on the environment.

Congress is open to considering new government incentives to accelerate development of alternative fuels and the infrastructure to deliver them. But lawmakers want a firmer commitment from auto companies that they plan serious change, which could also leverage new thinking in the fuels industry.

"Our hope is that with this commitment, fuel providers will have even more incentive to produce ethanol and other biofuels and install pumps to distribute them," the chief executives of GM, Ford and Chrysler said in a letter to members of Congress.

Renewable or biofuels are crop-based products that are mixed with traditional fuels. Experts say they burn cleaner and save energy compared to gasoline. However, the infrastructure for renewable fuels is mainly in the Midwest where much of the crop production occurs.