Offering utilities a chance to upgrade and expand coal-burning power plants, the Environmental Protection Agency announced Thursday that it plans to ease air pollution standards.

The "New Source Review" requirements attached to the Clean Air Act will allow energy producers the opportunity to make changes needed to reduce their emissions, EPA administrator Christine Todd Whitman said.

"EPA is taking actions now to improve NSR and thereby encourage emissions reductions," Whitman said in a statement. "NSR is a valuable program in many respects but the need for reform is clear and has broad-based support."

The news is sure to irk environmental groups, who say the new measures gut air pollution rules that force dirty, older plants to cut emissions by 95 percent.

The Clinton administration had filed lawsuits against a group of utilities and 51 power plants alleging that the plants were violating the Clean Air Act by making illegal modifications that produced more electricity and more pollution. Environmentalists say those suits will now be in jeopardy.

"With the release of this report, the administration dropped a dirty bomb and it's going to cost thousands of American lives," Buck Parker, executive director of Oakland, Calif.-based Earthjustice, an environmental law firm, said Thursday. "Utilities and refineries are going to have a very easy time of avoiding any type of New Source Review. It's a roadmap for how to avoid New Source Review."

But Whitman argued that the EPA's review of pollution controls "clearly established that some aspects of the NSR program have deterred companies from implementing projects that would increase energy efficiency and decrease air pollution."

The new plan will give utilities the power to expand production by raising the threshold at which they need to install new pollution controls.

The plan allows utilities to use pollution levels from any two consecutive years during the past 10 years to establish an emissions baseline to determine how much additional pollution will be allowed before the controls kick in.

Officials expect that expansions will use more modern, energy-efficient technologies and facilities that will reduce emissions.

Utilities are already threatened with heavy fines unless they spend tens of billions of dollars to more strictly control emissions of acid rain-causing sulfur dioxide, smog-causing nitrogen oxides and mercury, a toxic chemical that contaminates waterways.

With the changes, supported by Vice President Dick Cheney's energy task force, companies can now upgrade facilities without the threat of being sued, said one electricity trade group.

"At the end of the day, power plant operators need to be able to run their facilities without the perpetual threat of litigation," said Dan Reidinger, a spokesman for Edison Electric Institute, which represents investor-owned utilities.

Environmentalists and state attorneys general from the Northeast have said they would challenge in court any substantial weakening of the program, which they say will allow coal-burning plants to add millions of tons of additional pollution to the air. The Northeastern states say pollution from power plants in the Midwest drifts eastward.

The Associated Press contributed to this report.