The cities join an increasing number of states, including California and New York, and leading corporations choosing to follow the Kyoto lead even while their country doesn't.

They can act by using renewable energy and alternative fuels, placing tougher controls on auto emissions or building energy-saving green buildings.

"We reject the idea that is put forward by our national leaders in the United States that we have a choice to save the environment or save the economy," Nickels said on Tuesday on the sidelines of the 189-nation United Nations conference on climate change.

Bush pulled the United States out of Kyoto in 2001, arguing that the mandatory emissions cuts for some 40 industrial nations would hurt US growth and wrongly excluded developing economies like China and India.

And since then his administration has shown no sign of budging on accepting mandatory curbs, to the frustration of European leaders and environmental activists huddling in Montreal.

"Unfortunately, we are experiencing Category 5 denials by the Bush administration," said Jerome Ringo, who chairs the National Wildlife Federation in the United States and uses the term for the strongest hurricane rating.

Ringo said mayors, governors and congressmen are "filling the leadership vacuum left by the Bush administration."

CALIFORNIA LEADERSHIP

Cities, states and Congress are also showing that acting on climate change is a bipartisan effort, not one restricted to the Democrats who largely stand behind the Kyoto protocol.

California's Republican Gov. Arnold Schwarzenegger has won environmentalists' praise at the conference with progress on his ambitious plan to reduce greenhouse gases in the nation's most populous state 80 percent from 1990 levels by 2050.

Per capita carbon dioxide emissions in California are around half of the US average and have fallen 30 percent since 1975, while they have remained constant for the country.

"We are all part of the solution on climate change. The governor recognizes that, while California is only a piece of that, leadership is important and we can play that role," Alan Lloyd, California's secretary for the environment, said.

As nations debate in Montreal how to proceed after 2012, a bipartisan group of 24 US senators wrote a letter to Bush on Monday asking the administration to participate in talks in a "constructive way" and not block discussions on binding emissions.

Mayor Nickels hopes results on the local and state levels will eventually lead the United States back into the Kyoto protocol for post-2012.