The United States came under renewed criticism Tuesday as thousands of environmentalists and international officials hammered out rules for a global treaty to cut greenhouse gas emissions.

U.S. comments that it would resist any binding commitment to curb global warming by capping industrial emissions infuriated environmentalists, who accused Washington of trying to derail the U.N. Climate Change Conference.

"When you walk around the conference hall here, delegates are saying there are lots of issues on the agenda, but there's only one real problem, and that's the United States," said Bill Hare of Greenpeace International.

More than 8,000 environmentalists, scientists and government officials were attending the 10-day conference in Montreal. Some 120 environment ministers and other government leaders were expected to arrive next week for the final negotiations.

The conference is the first meeting of the 140 countries that ratified the Kyoto Protocol since the agreement was adopted in 1997. It is aimed at setting agreements on emissions cuts planned after 2012, when the second phase of the protocol begins.

The Kyoto agreement targets carbon dioxide and five other heat-trapping gases blamed for rising global temperatures and disrupted weather patterns. It calls on the top 35 industrialized nations to cut emissions to 5.2 percent below their 1990 levels between 2008 and 2012.

The United States, the world's largest emitter of polluting gases, has refused to ratify the agreement, saying it would harm the U.S. economy and is flawed by the lack of restrictions on emissions by emerging economies such as China and India.

President Bush called for an 18 percent reduction in the U.S. growth rate of greenhouse gases by 2012 and has committed $5 billion a year on science and technology to combat global warming.

Harlan Watson, chief climate control negotiator for the U.S. State Department, told a news conference that Washington would maintain its position of rejecting any calls for an international agreement that binds countries to emissions reductions after 2012.

Watson said the United States would continue voluntary efforts to curb global warming via science, technology and bilateral agreements with other nations. He said greenhouse gas emissions had gone down nearly 1 percent in Bush's first three years in office.

"We need to pursue our international efforts in a spirit of cooperation — not coercion — with a true sense of partnership," Watson said.

Alden Meyer of the U.S.-based Union of Concerned Scientists questioned the 18 percent reduction figure cited by the administration.

He said that as Americans upgrade to more energy efficient factories, cars and appliances, the emissions of carbon dioxide will decline. But economic growth per capita — without mandatory emissions caps — means the United States would likely see a 30-percent hike in greenhouse gas emissions over 1990 levels by 2012.

He applauded the Bush administration for its massive spending on science and technology to find less polluting alternative energy sources, but said the results won't hit the market quickly enough to deal with global warming.

Watson told The Associated Press in an interview Monday that the Bush administration does not blame global warming or climate change for extreme weather — including the hurricanes that ravaged the Gulf Coast states and much of the Caribbean and Yucatan Peninsula.

"There's a difference between climate and extreme weather," Watson said. "Our scientists continually tell us we cannot blame any single extreme event, attribute that to climate change."

This notion infuriates environmentalists, who point to myriad studies that they believe prove global warming is to blame for rising, warmer seas, melting Arctic glaciers and extreme weather conditions.

Environmentalists are pushing host Canada to round up industrialized nations for some sort of political agreement by the end of the conference which commits them to further goals and potential greenhouse gas cuts in the new phase of the Kyoto Protocol, which begins in 2013.

Canada's Environment Minister Stephane Dion said Monday that he would "welcome any idea" to get the United States on board.

"We cannot do without the Americans because they represent 25 percent of emissions, and an even greater percentage of the solution," he said.

British Prime Minister Tony Blair, meanwhile, said Tuesday he believed the United States would eventually come on board with mandatory emissions caps.

"I believe there will be a binding international agreement to succeed Kyoto when the Protocol expires in 2012 that will include all major economies," Blair said in a review of British energy policy.