California plans to sue the Bush administration next week to demand action on the state's request to restrict greenhouse emissions from cars and trucks.
Governor Arnold Schwarzenegger's office says the state has waited too long for a decision from the U.S. Environmental Protection Agency.
California wants to start implementing a 2002 state law that limits auto emissions of carbon dioxide and other gases linked to global warming. But it needs EPA's approval because the statute is stricter than federal clean-air standards.
California requested federal permission to enforce the state law in December 2005.
California's auto emissions law is a model for similar statutes passed in 11 other states.