WASHINGTON — An environmental group sued the Bush administration Tuesday over new rules to boost gas mileage requirements for sport utility vehicles and pickup trucks, saying the regulations do not go far enough.

The Sierra Club, which filed the lawsuit, joined 10 states and other environmental groups in challenging the rules, which would raise gas mileage requirements by 1.8 miles per gallon for the 2008-2011 model years to a fleetwide average of 24 mpg.

The administration released the new rules in March. The program, which implements gas mileage rules based on a vehicle's size, is expected to save 10.7 billion gallons of fuel, but detractors have said it only amounts to a few weeks of fuel.

With high gas prices on the minds of consumers, President Bush has also sought the authority to change the fuel economy program for passenger cars. A measure allowing the administration to begin the process is under consideration in Congress.

In the lawsuit, Sierra Club officials said the National Highway Traffic Safety Administration failed to follow the law requiring it to set fuel economy standards at the maximum feasible level, arguing it could have demanded more from automakers.

Pat Gallagher, director of the Sierra Club's legal program, said the new rules "underestimated the technologies and ignored important benefits, such as the ability to significantly reduce our global warming emissions."

The group also cautioned that the size-based standard could give automakers an incentive to avoid strict standards by building larger vehicles that qualify for lower fuel economy rules. The lawsuit was filed with the 9th U.S. Circuit Court of Appeals in San Francisco.

NHTSA spokesman Rae Tyson said the agency had not yet seen the lawsuit but the new rules were formulated "in a very careful and thorough and deliberate fashion" that considered comments from a wide range of groups.

"We are confident that the regulations that we finally came up with will be upheld in court," he said.

Tyson said the agency had to develop a standard "that is technically feasible and achievable without compromising safety and without doing serious damage to the American economy and we believe we found that balance."

Earlier this month, California and nine other states sued the government over the rules, contending NHTSA did not conduct a thorough analysis of the environmental benefits of fuel economy regulations and the impact of gasoline consumption on climate change.

Similar lawsuits have been filed by the Tucson, Ariz.-based Center for Biological Diversity and the Natural Resources Defense Council.

Source: Associated Press