For the second day in a row, Mr. Bush asked lawmakers to embrace his stalled "Clear Skies" Initiative, a plan for reducing mercury, nitrogen oxide and sulfur dioxide pollution from coal-burning power plants. He said it would improve upon the gains achieved since the passage of the 1990 Clean Air Act.
"By taking this action, and I urge Congress to take the action, we'll have more affordable energy, more jobs and cleaner skies," said the president, surrounded in the White House's East Garden by about 100 supporters from Congress, the private sector and elsewhere. "The legislation on the books is counterproductive. We've got to change it with good, common-sense legislation."
On Monday, Mr. Bush broadcast the same message at a power plant in Michigan.
His proposal calls for a cap-and-trade system. It would phase in caps on the emissions from coal-burning power plants that are major sources of two kinds of dirty, unhealthy air: nitrogen oxide, which causes smog, and sulfur dioxide, which causes soot and acid rain. It also would create the first controls on the plants' releases of mercury.
Utilities that exceeded the limits could purchase credits from other energy producers whose emissions are lower and who choose to sell their ability to pollute.
"What we're talking about is good for the working people of this country. What we're talking about makes sense for those who work for a living," Mr. Bush said. "By combining the ethic of good stewardship and a spirit of innovation, we will continue to improve the quality of our air and the health of our economy, and improve the chance for people to have a good life here in America."
Environmentalists said the Bush air pollution plan would weaken current limits under the Clean Air Act. And they criticize Mr. Bush for failing to address carbon dioxide, blamed by many for global warming, even though power plants are a chief source of those emissions.
"Even though it would be a reduction, it is significantly less than the Clean Air Act would require over time," said the National Audubon Society's Bob Perciasepe, former EPA assistant administrator for air during the Clinton administration. "And it doesn't do anything about carbon dioxide."
Eric Schaeffer, director of the Environmental Integrity Project and former chief of civil enforcement at the Environmental Protection Agency, called Clear Skies a "sham" because, he said, it would leave communities next to older power plants unprotected without any hope of cleaner air in the near future.
Clear Skies sets a long-term cap on emissions, but doesn't require anything from individual plants, he said. If a certain plant wants to avoid controls and "keep on showering its neighbors with sulfur dioxide," it can do so under Clear Skies by buying emission credits from a clean plant a thousand miles away.
Meanwhile, the dispute over Clear Skies is causing problems in the Senate for Mr. Bush's nominee to head the Environmental Protection Agency.
A third Democratic senator, presidential aspirant John Edwards, said Monday that he would join efforts to block the nomination of Mike Leavitt as EPA administrator. Those efforts seemed aimed more at White House environmental policies than at Leavitt himself.
"I've put a hold on the nomination to try to get the EPA to tell the truth about the safety of the air we breathe," said Edwards in a statement. He said that more than a year ago he and 43 other senators asked the EPA to conduct "a rigorous analysis" of the public health effects of administration proposals on clean air rules.
Democrats Sens. Hillary Rodham Clinton of New York and Joe Lieberman of Connecticut, who also is seeking the presidential nomination, previously had said they would put a hold on the nomination,
Clinton, who was the first to say she would block Leavitt's nomination, said she would not allow it to go forward until the administration responds more fully to a report that the EPA misled New Yorkers about the health risks from contaminated air in the aftermath of the World Trade Center terrorist attacks.
An EPA inspector general said he EPA, at White House request, provided misleading advisories about the potential risks. Administration officials have denied any intention to mislead.
Any senator can put a hold on a nomination, preventing it from being scheduled for a floor vote. Traditionally Senate leaders, no matter which party, have abided by such a request, although a nomination may still go through the committee process.
Mr. Bush announced his selection of Leavitt, a Republican known for seeking consensus on environmental issues and avoiding confrontation, on Aug. 11 to succeed Christie Whitman as head of the EPA.