It also contains a provision critics say could violate the 45-year-old U.S. embargo against Cuba.

The bill proposed by Sens. Byron Dorgan, D-N.D., and Larry Craig, R-Idaho, includes a 4 percent annual increase in fuel economy for new cars and trucks from 2012 to 2030.

By 2025, car and light-truck owners would save more than $30 billion a year, cut annual global warming pollution by some 500 million metric tons of carbon dioxide equivalent, and reduce U.S. oil dependence by up to 3 million barrels a day, the senators said.

The bill calls for incentives for renewable fuels, including ethanol ingredients besides corn.

The measure includes a provision to open Cuban waters to U.S. oil and natural gas companies, which some lawmakers say would skirt the Cuba embargo.

Sen. Mel Martinez, R-Fla., called that part of the proposal "bad policy."

Craig said Cuba's leadership would "probably change sooner rather than later."

Dorgan called the embargo "one of the greatest follies of American foreign policy."