At issue is a request the state made in 2005 for a waiver that would exempt it from the federal Clean Air Act, allowing California to more aggressively regulate automobile emissions as air pollutants.
"It's a priority for Californians to protect our environment, and if the federal government fails to act to protect our environment, we will take steps to do so ourselves," Schwarzenegger spokesman Aaron McLear told The Associated Press.
Schwarzenegger will send a letter Wednesday to EPA Administrator Stephen Johnson. The governor was to announce the state's intention to sue during a luncheon speech at the Milken Institute's 10th Anniversary Global Conference in Beverly Hills.
The EPA had delayed acting on the request because the agency maintained it did not have the authority to regulate the gases that contribute to global warming. The state's request was revived earlier this month when the U.S. Supreme Court decided that the EPA does have the authority to regulate greenhouse gases, a position that had long been rejected by the Bush administration.
On Tuesday, Johnson told senators that he had begun the formal process to act on California's request. That involves a public hearing May 22 in Washington and a public comment period that ends June 15.
But Johnson refused to set a timetable specifying when the agency would issue a decision on California's request.
"We will move expeditiously, but we are going to be moving responsibly," Johnson told the Senate Environment and Public Works Committee.
The 5-4 Supreme Court decision did not require the EPA to regulate greenhouse gases. But it does say the agency must show that carbon dioxide emissions are not a danger to public health if it chooses not regulate them under the Clean Air Act.
The committee's chairwoman, Sen. Barbara Boxer, D-Calif., said she expected the EPA to make a decision by the middle of the summer and would call agency officials back before her panel after the comment period had closed.
California's waiver is needed for the state to implement a 2002 state law that would require automakers to reduce emissions from cars and light trucks by 25 percent and from sport utility vehicles by 18 percent starting with the 2009 model year.
The waiver also carries implications for at least 10 other states that have adopted California's standard. Federal law allows states to choose between the federal and the California rules.