WASHINGTON - House Speaker Nancy Pelosi told the Environmental Protection Agency yesterday that Congress would scrutinize its decision to reject California's request to tighten rules on greenhouse gas emissions.

Pelosi said she disagreed with the agency's rationale for the decision and would support an investigation by a fellow California Democrat, Rep. Henry A. Waxman. He is seeking all documents related to the state's request for a waiver to implement fuel-efficiency rules for vehicles that it says will work faster than the federal government's.

"The actions of the EPA in denying the California request cannot help but raise serious questions about the support of the Bush administration for state efforts to safeguard the environment and the health of their residents," Pelosi wrote in a letter to EPA Administrator Stephen L. Johnson.

EPA's announcement Wednesday that it would bar California and at least 16 other states from regulating tailpipe emissions from new cars and trucks was swiftly criticized by state leaders and environmental groups.

Johnson said California's emissions limits were not needed because Congress approved energy legislation raising fuel-efficiency standards nationwide to an average of 35 miles per gallon by 2020. California officials say their state's law was tougher and would have an impact faster.

White House deputy press secretary Tony Fratto yesterday defended Johnson's decision.