The Bush administration has appealed a court ruling that the Environmental Protection Agency violated the federal Clean Air Act when it issued less stringent requirements to reduce mercury releases from power plants.

The Justice Department, in seeking a review of the decision, argued that the three-judge panel misinterpreted the federal clean air law and required "inappropriate and unnecessary emissions standards for power plants."

The states' lawsuit maintained that the EPA plan, allowing power plants to purchase emissions credits instead of making pollution reductions, creates mercury "hot spots" near some plants. Instead the states want all plants to be required to install the best available pollution controls, which could lead to mercury emission reductions of 90 percent or more.

Separately, a group of electric utilities also filed a petition with the full appeals court, asking for a review. The Utility Air Regulatory Group, argued that the EPA has the discretion to regulate emissions in a way it considers necessary and appropriate.

The group includes electric generating companies and trade associations representing power companies and coal interests.