They agreed to collaborate on research into cleaner-burning fuels and technologies, and look into the possibility of setting up a system whereby polluters could buy and sell the right to emit greenhouse gases. The idea is to use market forces and market incentives to curb pollution.
Environmental groups questioned the value of the agreement, calling it little more than a symbolic gesture.
California is looking to cut carbon dioxide - a byproduct of coal, oil and gasoline combustion - and other heat-trapping gases that scientists say are warming the planet. President Bush has rejected the idea of ordering such cuts.
