WASHINGTON - A strong federal law to combat global warming would be better than states passing their own measures as California did, Democratic Sens. Barbara Boxer and Dianne Feinstein agreed Tuesday as Boxer chaired her first hearing on climate change.

But when Feinstein introduced a global warming bill this month, criticism from California officials led her to drop language that would have pre-empted the state's first-in-the nation law capping greenhouse gas emissions, she said.

The language "became very controversial," Feinstein said in testimony before the Senate Environment and Public Works Committee that Boxer chairs. Gov. Arnold Schwarzenegger's office and environmental groups both voiced concerns about whether Feinstein's bill would reach the same strong standards set out in California law, something Feinstein believes it would.

Nevertheless, said Feinstein, "I think we need to grapple with a national standard so everybody plays with the same standards across the board."

"If we have a good system with good goals then one system is clearly the best," Boxer said.

Boxer called the hearing to get senators' views on climate change as Congress prepares to grapple with the issue. A number of senators - including several 2008 presidential hopefuls - endorsed imposing mandatory caps on greenhouse gas emissions that cause global warming.

Boxer and Feinstein both support that approach, though Feinstein has limited her bill to just the electricity sector - which accounts for about 33 percent of greenhouse gas emissions - while Boxer supports an economy-wide solution.

"The broad consensus of those who spoke is that the time for action is now," said Boxer. "I think that this is the moment where we will take a stand."