"There's no question that the way the court views the TVA case will affect the way we all think about these other cases," said Allen Franklin, chief executive of Atlanta-based utility Southern Co. .

At issue is how far a U.S. utility can go in enlarging or upgrading an old plant before it must invest in expensive new air pollution technology to control smog, acid rain and soot.

The Clinton administration sued nine Midwestern and Southern utilities in November 1999 to enforce the Clean Air Act's so-called "new source review" rule.

The rule exempts power plants and oil refineries built before 1977 from installing modern pollution controls unless major modifications are made to the plants.

The industry, which has bitterly opposed the pollution rule, claimed the regulations prevented more power plants from being expanded and limited energy supplies.

Franklin rejected the notion that Southern has idled its legal efforts because of the TVA case, but affirmed its importance.

"We're certainly not sitting on the sidelines waiting to see how this case turns out. But at the same time the way it turns out will impact the way we think going forward," he said in an interview.

Last week, EPA Administrator Christine Todd Whitman expressed similar thoughts, and was immediately criticized by green groups.

"If I were a plaintiff's attorney, I wouldn't settle anything until I knew what happened to that case," Whitman testified at a Senate hearing. "We should be getting a decision sometime in April, and that will, I think, determine whether other companies come to the table."

TVA is the nation's biggest public power producer, supplying electricity throughout the Southeast.

The government accused TVA of illegally modifying seven old coal-burning power plants without installing modern anti-pollution equipment. TVA contends the work was merely routine maintenance, and not any kind of major expansion that would trigger the federal requirement for stricter controls.

Other companies sued in 1999 were FirstEnergy Corp , Duke Energy Corp , Vectren Corp's Southern Indiana Gas & Electric Co, Dynegy Inc's Illinois Power, Cinergy Corp and American Electric Power Co .

The lawsuits sought civil penalties of up to $27,500 for each day of violation at each power plant.

But uncertainty over new source review has placed EPA's court actions to enforce the Clean Air Act in jeopardy, said Eric Schaeffer, the former director of EPA's Office of Regulatory Enforcement. Schaeffer recently resigned to protest the Bush administration's anti-enforcement stance.

He criticized Whitman for failing to push harder for settlements in the lawsuits.