Frustrated by the Bush administration's refusal to ratify the Kyoto Treaty, 132 US mayors have pledged to enforce its regulations in their own cities.
In a rejection of the government's position, which claimed it would be too damaging to the US economy to enforce tougher environmental restrictions, the group of bipartisan city leaders have vowed to try to meet Kyoto's main target - a reduction in greenhouse gases of about 7 per cent on the 1990 figure in less than 10 years.
The cities involved range from liberal centres such as Los Angeles, California, to strongholds of conservatism such as Hurst, in President Bush's home state of Texas. Between them they represent almost 29 million citizens spread across 35 different states.
They are united by the idea that even if the federal government will not sign-up to Kyoto, a difference can be made at a local level.
Across the country, the shift in policies required if the cities are to hope to meet their targets is already underway. In Seattle, whose mayor Greg Nickel is one of the organisers of the coalition, cruise ships that come in to dock are now required to turn off their diesel engines while resupplying and rely on electricity provided by the city. The mayor's office said that by the end of the year, Seattle's power utility, Seattle City Light, will be the only one in the country with no net emissions of greenhouse gases.
In Salt Lake City, the city authority has become Utah's largest buyer of wind power in order to meet its reduction target. In New York, the administration of Michael Bloomberg, which signed up last week, is trying to reduce emissions from the municipal motor fleet by buying hybrid-powered vehicles.
The mayor of low-lying New Orleans, Ray Nagin, a Democrat, told The New York Times that he joined the coalition because a projected rise in sea levels "threatens the very existence of New Orleans".
In Hawaii, the mayor of Maui County, Alan Arakawa, a Republican, said he joined because he was frustrated by the administration's failure to recognise the scientific consensus that climate change was happening because of human activity.
Nathan Mantua, of the Centre for Science in the Earth System at the University of Washington, which estimates the impact of global warming on the US north-west, said the coalition's efforts were probably of limited global impact. "It is clearly a politically significant step in the right direction," he said. "It may be an environmentally significant step for air quality in the cities that are going to do this, but for the global warming problem it is a baby step."
The coalition of mayors is not the only local initiative to reduce emissions of such gasses. Last November, nine states, led by New York's Governor, George Pataki, announced a system to cap and trade greenhouse gas emissions. Under the Regional Greenhouse Gas Initiative (RGGI), industries covered by the schemes will be given allocations in units of one ton of carbon dioxide produced. Polluters could then either reduce their emissions or buy allocations on a market from others. In the US, sulphur dioxide and nitrogen oxide emissions, which cause acid rain and smog, are federally regulated and traded, but there is no federal regulation of carbon dioxide.
A White House official said that joining the Kyoto Treaty, which came into effect last February, would have cost the US economy five million jobs.