House and Senate negotiators are poised to seal a deal on an energy bill that would strengthen fuel economy standards for the first time in three decades.

The measure also would require billions of gallons of alternative fuels to be incorporated into gasoline over the next 13 years, according to staffers and draft language being circulated.

The compromise, which is expected to land in the Office of the Legislative Counsel for drafting very soon, reconciles the major differences between separate versions of energy legislation that passed each chamber earlier this year.

It would require the nation’s fleet of vehicles to meet a 35 miles-per-gallon fuel efficiency standard by 2020 and would mandate 20.5 billion gallons of ethanol and other biofuels to be in use by 2015.

With crude oil nearing $100 per barrel and gasoline above $3 per gallon, an agreement on corporate average fuel economy (CAFE) standards is perhaps the most significant development to come out of the informal energy bill negotiations, which have been under way for weeks.

Sen. Dianne Feinstein, D-Calif., who championed the fuel economy standard in the Senate, said negotiations were ongoing, but added, in a statement, that “we hope to have something that everybody can support that takes a major step forward.”

Rep. John D. Dingell, D-Mich., chairman of the House Energy and Commerce Committee, was still reviewing the compromise language Wednesday, sources said. But in a letter sent to House Speaker Nancy Pelosi, D-Calif., on Nov. 13, Dingell – who initially supported a less stringent fuel economy bill in the House — indicated that a compromise based on the Senate version was possible.

While the emerging CAFE provision does not set separate standards for cars and trucks, as the House bill would have, it allows for the two vehicle types to have separate fuel economies by assigning a fleet-wide fuel economy average that incorporates both.