WASHINGTON – President Bush, prodded by a Supreme Court ruling, said Monday his administration will decide how to regulate pollution from new motor vehicles by the time he leaves office.

Bush signed an executive order directing federal agencies to craft regulations that will “cut gasoline consumption and greenhouse gas emissions from motor vehicles.” He ordered the agencies the departments of Transportation, Agriculture and Energy and the Environmental Protection Agency to have the rules in place by the end of 2008.

The announcement came as gasoline prices hit a new record. The average national price of a gallon of gas reached $3.07 on Monday, above the previous peak of $3.06 set soon after Hurricane Katrina hit at the end of August 2005.

“When it comes to energy and the environment, the American people expect common sense and they expect action,” the president said in a Rose Garden appearance before reporters. “We’re taking action by taking the first steps toward rules that will make our economy stronger, our environment cleaner and our nation more secure for generations to come.”

What those rules would look like was anything but clear.

White House press secretary Tony Snow said the president’s position opposing mandatory emissions caps has not changed. While recognizing that greenhouse gases are a serious contributor to climate change, Bush has said that anything other than a voluntary approach would unduly harm the nation’s economy.

“The question is: do you try to set up a mandatory system or do you try to set up an innovation-based system?” Snow said. “The president prefers innovation.”

But the Democratic-controlled Congress is considering a number of bills that would impose a cap on emissions of carbon dioxide, the leading gas linked to global warming, and a carbon trade system.

“It appears that the president wants to run out the clock to the end of his term without addressing our energy needs,” said House Speaker Nancy Pelosi, D-Calif.

Last month, the Supreme Court declared that carbon dioxide and other greenhouse gases qualify as air pollutants under the Clean Air Act and thus can be regulated by the EPA. The court also said that the “laundry list” of reasons the administration has given for declining to do so are insufficient, ruling that the EPA must regulate carbon dioxide if it finds that it endangers public health.

EPA admistrator Stephen Johnson said a draft proposal should be ready by fall, and that it will include a finding on whether carbon dioxide is a health threat. He suggested there could be no regulation if no threat is found, or if the agency determines there is “some other reason and rational explanation for why it was not necessary to regulate.”

Bush said that, in writing any rules, agency officials must take into account the views of the general public, scientific knowledge, available technology, the cost and the impact the new rules would have on safety.

All this left environmentalists and Democrats on Capitol Hill concerned. A report this month from a United Nations network of over 2,000 scientists estimates the world must stabilize the amount of greenhouse gases in the atmosphere within eight years to keep global temperatures from spiking to disastrous levels.

The environmental group Environmental Defense said the effort “will fall far short of fixing the climate problem” without mandatory caps on carbon emissions.

“Whether EPA will lead the fight against global warming or lead us to a hotter planet remains to be seen,” said Environmental Defense President Fred Krupp.

Bush and administration officials said the process will take time because it is so complicated. Johnson indicated that _ at the least _ the new rules could implement the president’s plan for reducing gas consumption by 20 percent over 10 years.

As announced in Bush’s State of the Union address in January, this plan envisions increasing the country’s use of alternative fuels to 35 billion gallons by 2017. It also would give the administration the ability to rewrite mileage rules for passenger cars, which now must meet a two-decades-old fleet average of 27.5 mpg, so that they are based on a vehicle’s size.

Bush says this is a safe way to boost car mileage, but critics say it could spur the production of more gas guzzlers. It is less ambitious than a bill approved earlier this month in a Senate committee, which would raise the nationwide fleet fuel economy to an average of 35 mpg by 2020, and others being drafted in the House.

Johnson said that since the Supreme Court decision gave the EPA “significant latitude” as to how to comply with its regulatory obligations, the administration interprets that as the authority to implement Bush’s proposal without congressional approval.

However, he stressed that legislation to Bush’s liking is preferable.