WASHINGTON -- Hidden in the nation's current debate over energy is one measure that supporters say could do more than any other to conserve fuel - the loophole that lets vans and sport utility vehicles escape higher fuel efficiency standards.

Making those vehicles adhere to higher standards "would save an amount of fuel equal to, if not greater than, the projected production from the Arctic National Wildlife Refuge," said Rep. John Olver, D-Mass., sponsor of a House bill that would impose tougher standards on SUVs.

But Olver and others who want to close the loophole acknowledge that their efforts won't pay off any time soon, and say that the way Washington handled the issue last week underscores why.

The White House only called for further review of the "corporate average fuel economy" standards that automakers are required to meet. Democrats also avoided the issue. In their "Principles for Energy Prosperity" report, House Democrats chided the White House for paying lip service to conservation, but called for fuel efficiency standards only "in accordance with requirements and conditions of existing law."

And a soon-to-be-released study of CAFE standards cited in the White House energy plan and expected to serve as a guide for lawmakers increasingly is seen as written in the auto industry's favor.

Frustrated opponents of the loophole say their efforts are blocked by the powerful auto industry lobby, which has tremendous sway in both parties.

As a result, an energy crunch that many people thought might create the first opening in years for ratcheting up fuel economy standards instead appears unlikely to alter the status quo.

The White House released its energy plan Thursday, amid severe power shortages in the West and rising fuel costs across the country that have pushed gasoline prices above $2 per gallon in some locations.

But the politicians opposing stricter fuel economy laws may be simply trying to give their constituents what they want. There was new evidence Friday that Americans' appetite for big vehicles continues to soar. A Transportation Department report released Friday showed that the average fuel economy among new cars this year is 24.5 miles per gallon - tying 1999 for the lowest mark since 1980.

The study estimates cars for the 2001 model year are getting an average 28.7 miles per gallon, but light trucks are getting just 20.9. The latter category, which includes minivans and sport utility vehicles, accounts for nearly half of the passenger vehicles sold in the United States.

CAFE standards were signed into law by President Ford in 1975. They require each auto company to produce cars with an average fuel economy of 27.5 miles per gallon. But the standard for light trucks is only 20.7 miles per gallon.

The auto industry argues that forcing SUVs and minivans to meet the higher standards would add substantial cost to, and reduce the performance of, a class of vehicles that has exploded in popularity over the past decade.

Conservationists say lawmakers who carved out the exception for light trucks never envisioned a wave of gas-guzzling SUVs and minivans. They say that closing the loophole would reduce U.S. oil consumption by 1 million barrels a day and prevent 187 million tons of carbon dioxide from entering the atmosphere.

In their dueling energy proposals, both parties addressed fuel economy standards, but mainly by proposing tax incentives for consumers who buy hybrid cars fueled by a combination of gas and electricity.

Many people were surprised that President Bush called for the transportation secretary to review CAFE standards. For the past six years, the Transportation Department wasn't allowed even to consider the issue, under rules attached to the agency's annual funding bill by auto industry allies in Congress.

"There are a lot of people who never imagined President Bush would even utter the word `CAFE,'" said Daniel Becker, director of the Sierra Club's global warming and energy program.

But the White House report was careful to spell out its goal of boosting efficiency "without negatively impacting the U.S. automotive industry."

"To see that language in there lessened any anxiety on our part," said Greg Martin, a spokesman for General Motors in the company's Washington, D.C., office.

On Capitol Hill, CAFE standards have been debated almost every year since they were introduced, but there has never been enough support to prompt any changes.

The issue is unusual in that it does not necessarily divide members along party lines. This year, for instance, Sens. Dianne Feinstein, D-Calif., and Olympia Snowe, R-Maine, are co-sponsors of a bill that would close the SUV loophole. A similar measure in the House also has bipartisan support.

There is entrenched opposition from Republicans who oppose federal regulation, Democrats supported by auto unions and almost any member from a state where oil is produced or cars manufactured.

Last year, Sen. Dianne Feinstein, D-Calif., and other proponents of reform gathered enough momentum to force a compromise. There would be no immediate changes, but opponents agreed to the creation of an independent National Academy of Sciences committee to study the issue. That panel's report is due in July.