SACRAMENTO, Calif. -- Gov. Arnold Schwarzenegger's efforts to position himself as a leader on climate change while maintaining support from business leaders has created an election-year dilemma that threatens to undermine his environmental credentials.

The Democratic majority in the Legislature plans to send him a bill this month that would create the country's first law capping greenhouse gas emissions from refineries, power plants and other industrial sources. He has asked for several pro-business changes to the bill that Democrats and environmentalists complain would severely weaken it.

Schwarzenegger has made global warming his signature environmental issue and is eager to sign a climate measure before he faces the state's Democratic-leaning electorate in November. It also would be another way for him to set himself apart from President Bush, who has opposed regulating global warming gases and is deeply unpopular in California.

"He hopes to have a bill on his desk this year that he can sign," spokesman Darrel Ng said, "but he wants to make sure it can be in a way that protects the economy and the environment."

At the same time, the Republican governor must tread carefully in the face of criticism from his own party for even considering signing legislation that businesses oppose.

"This noble goal of reducing greenhouse emissions and making energy use more efficient could backfire," said Dorothy Rothrock, a spokeswoman for the California Manufacturers and Technology Association. "It could hurt the economy and drive emissions outside California, thereby not improving the situation."

Schwarzenegger's opponent, Democratic state Treasurer Phil Angelides, said the changes Schwarzenegger has requested would create only a voluntary plan: "He's trying to gut this bill so he can claim an election-year victory, and the people of California and the environment will be left holding the bag for yet another broken promise."

A veto on a bill that is likely to be popular with the centrist voters Schwarzenegger needs in November could leave him vulnerable, despite the pro-environment record he has built since becoming governor in 2003. In June 2005, Schwarzenegger issued an executive order calling for the state to reduce greenhouse gas emissions to 2000 levels by 2010, 1990 levels by 2020 and to 80 percent below 1990 levels by 2050.