President Bush responded to a Supreme Court ruling by ordering federal agencies to find a way to begin regulating vehicle emissions by the time he leaves office.
In a Rose Garden announcement, Bush said he wanted to move ahead, pending any separate legislative approaches. The new rules will "cut gasoline consumption and greenhouse gas emissions from motor vehicles," he said.
But the Bush executive order telling several agencies to finish the work by 2008 also said they must take into account the views of the general public, the impact the new rules would have on safety, scientific knowledge, available technology and the cost. Bush's term ends Jan. 20, 2009.
"This is a complex legal and technical matter and it's going to take time to fully resolve," he said.
The agencies involved include the departments of Transportation, Agriculture and Energy and the Environmental Protection Agency.
Last month, the high court rebuked his administration for its inaction on global warming. In a 5-4 decision, it declared that carbon dioxide and other greenhouse gases qualify as air pollutants under the Clean Air Act and thus can be regulated by the Environmental Protection Agency.
The court also said that the "laundry list" of reasons the administration has given for declining to do so are insufficient, and that the agency must regulate carbon dioxide, the leading gas linked to global warming, it finds that it endangers public health.
Democrats who control Congress have been pressuring the administration to say when it will comply with the high court's ruling and decide whether to regulate carbon dioxide. It was unlikely they would be satisfied with the lengthy process laid out by the president.
Bush has said previously that he recognized the serious environmental problems created by such emissions and other so-called greenhouse gases. But he has urged against anything other than a voluntary approach to curbing emissions, saying regulations could undercut economic activity.
There were few details immediately available about how the rules might look, but White House press secretary Tony Snow said Monday that the president's position has not changed.
"The market-based approach seems to work," Snow said. "The question is: Do you try to set up a mandatory system or do you try to set up an innovation-based system? The president prefers innovation."
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. "It's time for this administration to join with the mainstream of American businesses and support a cap on carbon."
In his State of the Union address in January, Bush set a goal of reducing gas consumption by 20% over 10 years. Under his plan, this would be accomplished by increasing the use of alternative fuels to 35 billion gallons by 2017 and boosting fuel efficiency standards in new vehicles.
The president said Monday that the agencies should use this so-called "20-in-10 plan" as a starting point for the new regulations, while saying he still wants Congress to approve the plan legislatively.
"When it comes to energy and the environment, the American people expect common sense and they expect action," Bush said. "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."
Stocks of some ethanol-related companies rose Monday.