The Berkeley City Council voted late Tuesday to draft a proposal by next spring that will put stickers on gas pumps citywide to warn consumers that burning fuel contributes to global warming.
San Francisco is drafting a similar ordinance that the city's Board of Supervisors could vote into law by March. The proposals in the liberal Bay Area cities are thought to be the first of their kind in the U.S.
Supporters of Berkeley's measure hope that simply putting the labels in front of consumers will motivate them to drive less. One environmental group compares the labels to health warnings on cigarette packages.
But the Western States Petroleum Association, an oil-industry lobbying group, said the plan imposes "onerous restrictions" on businesses and "compels speech in violation of the First Amendment of the United States Constitution."
Implementing the labeling program could cost up to $20,000 the first year, and the head of the city's chamber of commerce said that money could be better spent.
Two council members voted against the plan.
Berkeley's environmental improvement efforts date back more than a century. In 1910, the famously liberal city was the first to put police officers on bicycle patrols.
Over the past 25 years, Berkeley has led efforts to ban Styrofoam and convert city vehicles to operate on biodiesel. The city also moved forward with a voter-approved plan to slice greenhouse gas emissions by a third from 2000 levels by 2020.