Siding with a Virginia-based energy industry coalition, the U.S. Court of Appeals for the District of Columbia Circuit on Friday said the states' regional program to reduce haze was too similar to an Environmental Protection Agency approach that the same court threw out three years ago.

States have been allowed under EPA rules to band together to figure out a better plan to reduce the haze.

Utah, Arizona, Oregon, New Mexico and Wyoming took up the task. Former Utah Gov. Mike Leavitt helped to lead the group of states from 1992-96 to come up with a market-based plan.

But the court on Friday ruled the regional plan wasn't better and, in fact, was too much like the one the court already decided was inadequate.

The ruling sided with arguments presented by the Center for Energy and Economic Development, a coal, rail and utility industry group that argued it was better to have no regulatory controls on polluting utilities than to single out the older ones for retrofit.

States are still assessing the ruling's impact and will need time to figure out a new approach, said Joseph Mikitish, an Arizona assistant attorney general who represented the five states and two others that supported the efforts.

''We need to go back to the drawing board,'' he said Friday night.

Rick Sprott, director of the Utah Division of Air Quality, said Tuesday that air-quality officials from the Western states were wondering what to make of the court ruling.

"The reasoning the court used is a little puzzling to a lot of folks," he said. Some attorneys have told him the regional approach is dead, but others say it's not.

The court agreed with the EPA that the Clean Air Act lets states develop pollution-trading programs that rely on market forces to cut haze regionally.

"There's been over 15 years of work put into this," Sprott said. "There are a lot of us going to be thinking how this can be salvaged."

By mid-April the EPA is scheduled to issue regulations on cleanup requirements for power plants and other industrial sources of haze in national parks.

Vickie Patton, an attorney for Environmental Defense, called the court's decision ''another chapter in the coal industries' efforts both in the courts and in the Congress to weaken clean air protections for our national parks.''

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The Associated Press contributed to this story.