Hoping to follow the Northeast's lead, three western states are trying to forge an agreement to cut greenhouse gas emissions from the region's power plants by 2020.

A day after nine northeastern states pledged to reduce local electric utilities' carbon dioxide pollution by 10 percent over 15 years to combat global warming, California officials said they hoped to outpace their eastern counterparts in a yet-to-be-negotiated pact with Oregon and Washington. Representatives of the three western states plan to meet in Sacramento in mid-September to hash out the details.

"We're making sure we have a uniform standard among the states in working toward greenhouse gas emissions," said Jon Myers, spokesman for California's Department of Environmental Protection. "California has a history for setting the bar a little higher."

The move on both coasts to regulate emissions of heat-trapping gases from fossil fuels highlights the extent to which states are taking the lead on climate-change policy. The Bush administration has refused to impose mandatory limits on carbon dioxide.

"The states are doing what the federal government should be doing," said Anthony Wexler, who directs the Air Quality Research Center at the University of California at Davis. "This is fantastic."

Under an agreement reported Wednesday by the New York Times, states including Connecticut, Massachusetts, New York and New Jersey devised a market-based system to first freeze and then reduce emissions from more than 600 electric power plants. The pact, which has been in the works for two years, would be the first of its kind and would let individual facilities trade pollution credits.

The participants in the regional pact, which also includes Delaware, Maine, New Hampshire, Rhode Island and Vermont, outlined the deal Wednesday as part of an invitation to a Sept. 21 meeting in Boston to debate the proposal. The pact would cap emissions at 150 million tons of carbon dioxide a year beginning in 2009. By 2015, states would have to adopt steeper cuts to meet 2020 emissions target.

California hopes to bring its greenhouse gas emissions down to 1990 levels by 2020, and then cut carbon dioxide to 85 percent of 1990 levels by 2050.

One Northeast official who worked on the pact but asked not to be identified said while the proposed emissions cuts were modest, they are "very practical and doable." The official added: "This is a big step forward."

Western state officials have attended meetings with their eastern counterparts, the official added, to try to develop a complementary emissions-trading system.

"We'll probably link them together," the official said. "There are a lot of states interested in what we're doing."

James L. Connaughton, who chairs the White House Council on Environmental Quality, said while he had yet to examine the plan's details he applauded the idea of a market-based pollution-trading system.

"We welcome all efforts to help meet the president's goal for significantly reducing greenhouse gas intensity by investing in new, more efficient technologies," Connaughton said. "We believe it is a better approach than regulatory mandates that would increase already high energy bills . . ., put people out of work or achieve reductions simply by buying more energy from and shifting emissions to other states."

Edison Electric Institute spokesman Dan Riedinger, whose group represents some of the nation's largest utilities, said consumers may face higher energy bills under the northeastern pact.

"The details of the plan are still sketchy at this point. However, utilities in the affected states have some concerns about the potential impacts on their customers," Riedinger said. "Make no mistake, a plan like this has the potential to have a significant impact on electricity prices in those states."

Some advocates of the pact, such as UC-Davis's Wexler, said the nine states would have to make sure they did not undermine cuts in their own states by buying electricity from out-of-state polluters.

"It's headed in the right direction, but the devil's in the details," Wexler said.

It remains unclear whether the utilities industry or administration would challenge such state initiatives. California is seeking to limit greenhouse gas emissions from cars, for example, and just this week the administration included language in new fuel economy standards saying that "a state law that seeks to reduce motor vehicle carbon dioxide emissions is both expressly and implicitly preempted."

A White House official who spoke on the condition of anonymity said under federal law the U.S. government, not the states, sets fuel economy standards. California can regulate carbon dioxide from cars only if it does not constitute a new fuel economy standard.