The Obama administration and leading power companies are going before the Supreme Court in an effort to block a global warming lawsuit aimed at forcing cuts in greenhouse gas emissions.

The justices are hearing arguments Tuesday in the court's second climate change case in four years. A half-dozen states, New York City and three land trusts sued four private utilities and the Tennessee Valley Authority over emissions of carbon dioxide from plants in 20 states. The lawsuit says carbon dioxide, which is produced when coal, gasoline and other fossil fuels burn, is one of the chief causes of global warming.

The administration and the companies say federal courts should not set environmental policy. The administration says the Environmental Protection Agency is developing regulations that would accomplish what the states are seeking.