Washington ? The Bush administration announced a modest increase Thursday in fuel economy requirements for sport utility vehicles, minivans and small trucks, beginning with the 2005 model year.

The change, which will become final after a 60-day comment period, represents the first tightening of motor vehicle fuel use since 1996, when Congress imposed a freeze on the federal fuel economy requirements on automakers.

The Transportation Department rule will require fleet-average fuel economy for so-called “light trucks” — SUVs, pickup trucks and minivans — to increase 1.5 miles per gallon over three years beginning with new vehicles coming into showrooms in late 2004.

Transportation Secretary Norman Mineta said the new requirements would “save 2.5 billion gallons of gasoline and improve the environment.”

But environmentalists scoffed at what they called a “minuscule” tightening of fuel economy requirements on automakers.

“If you measure the fuel savings in gallons you’ve got a trivial amount,” said Daniel Lashoff of the Natural Resources Defense Council.

The country uses about 19 million barrels of oil a day, about 40 percent of which is used by motor vehicles. There are 42 gallons to a barrel. Motor vehicles account for about a fifth of the carbon dioxide emissions linked to climate change.

Automakers now must meet a fleet average fuel economy of 20.7 mpg for SUVs, minivans and pickups. The proposed requirement will gradually ratchet that up to 22.2 mpg between the 2005 and 2007 model years.

The rule for other passenger vehicles will remain 27.5 miles per gallon.