On Thursday, as news was leaking out that Russia was likely to ratify the Kyoto global warming treaty, a group of U.S. business executives was discussing climate policy as they lunched on chicken and avocado sandwiches in Washington's St. Regis hotel.

One of them, Lee Califf, government affairs manager for Alcoa Inc., said the news meant that he has to reassess what carbon emissions reductions Alcoa will have to make in countries around the globe where the company has plants.

"Nobody seems to have a very clear idea of what this means for the United States," Califf said later, adding that even in the absence of U.S. regulation to limit greenhouse gases thought to be fueling the planet's warming trend, "We're going to have to do some of this stuff."

Assuming Russia's State Duma, its lower house of parliament, ratifies the 1997 accord on global climate change, the Kyoto treaty will take effect 90 days later in 126 countries, including the European Union, Japan and Canada. Under its terms, the 33 industrial countries that have signed will have to cut emissions of six greenhouse gases by 5.2 percent between 2008 and 2012, compared with 1990 levels.

But critics and proponents say the Kyoto treaty is more important for what it signals than what it would achieve, seeing that the gains over its four-year life would reduce global temperatures only 0.2 to 0.25 degrees Fahrenheit by 2100. Temperatures are expected to rise between 2.5 and 10.4 degrees Fahrenheit over the next century, according to the United Nations' Intergovernmental Panel on Climate Change.

"It sends a strong message that limits on heat-trapping gases are coming around the world," said David B. Sandalow, an environmental scholar at the Brookings Institution who served under President Bill Clinton.

American firms operating in participating countries will have to follow stricter rules and will not be able to count emissions cuts at their U.S. plants toward overseas targets, something they would have been able to do if the Bush administration had not opted out of Kyoto in 2001.

That does not mean, Califf said, that U.S. firms will push for legislation limiting greenhouse gases anytime soon.

"There aren't many companies lobbying Congress in favor of McCain-Lieberman," he said, alluding to a bill sponsored by Sens. John McCain (R-Ariz.) and Joseph I. Lieberman (D-Conn.) that would establish a program to cut carbon emissions to 2000 levels by 2010. The bill would set an overall cap on emissions while allowing individual companies to buy and sell pollution credits, in the same way Kyoto allows signatory countries to buy and sell emissions allowances.

McCain-Lieberman, which the White House opposes, fell short of a majority in 2003, with 43 aye votes in the Senate. But Eileen Claussen, president of the Pew Center on Climate Change who chairs the corporate-government policy group to which Califf belongs, said Russia's likely approval "ups the ante" for U.S. firms as well as American lawmakers.

"It just makes it all the more real for the private sector," she said.

Europe has moved ahead with a carbon emissions trading system without the United States, kicking off a program in January that affects 12,000 installations across the continent. European countries traded 2.5 million tons of emissions allowances last year, according to the New York-based emissions trading firm Natsource. Global carbon dioxide trading rose from 29 million tons in 2002 to 78 million tons last year and is expected to double again this year.

The Europeans are also placing political pressure on the United States. Last month, British Prime Minister Tony Blair, who is making global warming a centerpiece of the upcoming G-8 summit he will chair, called it "the world's greatest environmental challenge." A British Embassy spokesman said Friday his country "remains committed to re-engaging the U.S. by keeping climate change on the U.S.'s agenda."

The Bush administration has focused its efforts on climate change research and technology development, saying it opposes mandatory carbon emissions limits because such rules would cost jobs. James L. Connaughton, who chairs the White House Council on Environmental Quality, said the administration instead is promoting fuel and appliance efficiency standards and building codes that will conserve energy.

"The administration strongly opposes any treaty or policy that would cause the loss of a single American job," Connaughton said. "The greatest progress in greenhouse gas emissions reductions will come from transformational technologies."

Faced with opposition in the White House and Congress, advocates such as Claussen are focusing on moving beyond Kyoto and coming up with alternative steps to reduce greenhouse gas emissions. Claussen said her group, which includes representatives from Toyota and BP as well as Brazil and China, hopes to issue a proposal next year.

The National Commission on Energy Policy, a 17-member bipartisan panel funded mainly by the William and Flora Hewlett Foundation that includes American government, labor, industry and environmental officials, is planning to release climate policy recommendations as part of an energy plan it will issue in December.

"No politically realistic American policy advocate is looking for ways to get back into Kyoto," said William K. Reilly, who was Environmental Protection Agency administrator under President George H.W. Bush and now co-chairs the commission. "The challenge really is to create a domestic policy that has some credibility and slows emissions enough to begin to address the problem and ease international pressure."

Ultimately, domestic developments might have more of an impact on U.S. policy, such as the decision by 10 Northeastern and mid-Atlantic states to develop a cap-and-trade carbon emissions program, which is due to be unveiled next spring. California is drafting standards to reduce automobile greenhouse gas emissions by 30 percent, and New York may follow. Seventeen states, including Texas, have renewable energy requirements for electricity production.

"At some point, industry's going to throw up its hands and say we don't want to be regulated by 35 different states," said Claussen, who also served in the Clinton administration and predicted this would influence "how Congress will move on this, no matter who is president."

For now, however, Kyoto opponents in America are confident they can fend off legislated emissions curbs. Myron Ebell, director of global warming policy at the Competitive Enterprise Institute, said Russia's "decision doesn't change any votes in the Senate."