President Bush is poised to change course and announce as early as this week that he wants Congress to pass a bill to combat global warming, and will lay out principles for what that should include.
Specifics of the policy are still being fiercely debated, but Bush administration officials have told Republicans in Congress that they feel pressure to act now because they fear a coming regulatory nightmare. It would be the first time Mr. Bush has called for statutory authority on the subject.
"This is an attempt to move the administration and the party closer to the center on global warming. With these steps, it is hoped that the debate over this is over, and it is time to do something," said an administration source close to the White House who is familiar with the planning and who said to expect an announcement this week.
The source requested anonymity to be able to speak on a sensitive matter still under debate. Given the arguments at the White House over the extent of the action to take, it is not clear exactly what Mr. Bush will propose, the adminstration source said.
Still, Republican members of Congress who were briefed last week let top administration officials know that they think the White House is making a mistake, according to congressional sources and others familiar with the discussions. Opponents said Mr. Bush could be setting off runaway legislation, particularly with Democrats in control of Congress.
White House spokeswoman Dana Perino would not say whether an announcement is imminent. She said discussion has continued on how to follow up on Mr. Bush's call at the Group of Eight summit last year for the U.S. to lead on a post-Kyoto Protocol worldwide framework.
The administration also is trying to head off what it sees as a regulatory disaster. Environmentalists say greenhouse gases can be regulated under existing rules under the Clean Air Act, the Endangered Species Act or the National Environmental Policy Act, and have filed lawsuits to try to force action. The Bush administration and others want to avoid a web of rules and regulations for businesses.
"The embedded regulatory trajectory that we're on is a train wreck," Mrs. Perino said. "For those who want reasonable and responsible action, it is worthwhile to have a constructive conversation as we work to keep the developing nations in this process in a way that will work to solve the problem without harming the economy."
She said the administration's discussions, both internally and with Congress, are building toward an expected debate on climate change in the Senate in June and toward the next G-8 meeting in July, when the U.S. would like to have a more specific conversation about goals for cutting greenhouse-gas emissions.
At the end of this week, U.S. officials will be in Paris for a meeting with officials from other major economic powers, where climate change is expected to be on the table. Sources in the administration and in Congress say this meeting explains the White House push.
Mrs. Perino, though, stressed that the White House does not expect countries to come to the meeting with specific proposals.
Many scientists say humans are contributing to climate change through increased carbon dioxide emissions from industry, power generation, automobiles and other sources. Some governments, including European nations, have enacted rules to try to limit their emissions, though opponents say those rules end up hurting their economies without much environmental benefit to show for it.
With Sens. John McCain, Barack Obama and Hillary Rodham Clinton, the remaining major presidential candidates, all favoring new controls on greenhouse-gas emissions, Mr. Bush could be trying to lay the groundwork for the next president.
All three candidates are on record in favor of a cap-and-trade system, such as the Europeans have. The system sets an overall limit on carbon emissions and allows polluters to buy credits from companies that stay below their carbon targets.
The congressional and administration sources said it's not clear whether Mr. Bush will go that far this week.
But Brian Kennedy, spokesman for the Institute for Energy Research, said Mr. Bush should realize that the U.S. is already ahead of the Europeans.
"U.S. taxpayers are already spending more than $40 billion a year to address climate change, and to date we're achieving better results than the Europeans are under a bureaucratic regulatory framework," he said. "That should be kept in mind before any rash — or political — decisions are made inside the White House. Excessive regulations would come with significant economic consequences and additional costs for consumers."
Christopher C. Horner, author of "The Politically Incorrect Guide to Global Warming," said the Bush administration should have seen the regulatory problems long ago and that the president is trying to solve them the wrong way.
"There's a way to responsibly do this, but calling for a bill isn't it. Democrats — and all presidential candidates — desperately want Bush to take ownership of the issue before he goes, leaving them free of the burdens of responsibility for their rhetoric," Mr. Horner said.
He said Mr. Bush should have been spending the past two years pointing out that even as the U.S. reduces the rate of growth of carbon emissions, it is taking manufacturing jobs from Europe. Nations that adopted strict carbon emissions are facing economic consequences while finding the goals impossible to meet, he said.
"The U.S. is the world leader in reducing the rate of growth of CO2 emissions while also growing its economy — faster on both counts, as with population as well, than its principal antagonist, Europe, which is suffering for reasons of political 'face' under a failed scheme that the Democrats and McCain amazingly want to burden us with," he said.
James L. Connaughton, chairman of the Council on Environmental Quality, and Keith Hennessey, a domestic policy adviser to Mr. Bush, got an earful Wednesday when they briefed House members on the options the White House is considering.
One person familiar with the meeting said several members, including Republican Reps. John Shimkus of Illinois and F. James Sensenbrenner Jr. of Wisconsin, told the White House it was making a mistake if it called for congressional action.
Spokesmen for both congressmen said their bosses didn't want to be interviewed about the meeting, which they regarded as private. Steve Tomaszewski, a spokesman for Mr. Shimkus, said the congressman's exchange with administration officials was intended to let them know the prospects under a Democrat-controlled House.
"He was emphasizing that whatever proposal the administration might be discussing would not be received favorably by the majority in Congress," Mr. Tomaszewski said. "The speaker is pretty much focused on a cap-and-trade, and anything less that you might propose would likely not be received favorably. Small steps aren't what they're looking at right now."