WASHINGTON - The U.S. Supreme Court is set on Wednesday to hear a bid by three Republican-led states and several energy companies to block an Environmental Protection Agency regulation aimed at reducing ozone emissions that may worsen air pollution in neighboring states.

Ohio, Indiana and West Virginia, as well as pipeline operators including Kinder Morgan, power producers and U.S. Steel Corp, are seeking to avoid complying with the EPA's "Good Neighbor" plan restricting ozone pollution from upwind states, while they contest its legality in a lower court.