Mike Leavitt, head of the Environmental Protection Administration, said the plan would require power plants to use technology or chemical processes to meet new targets for reducing mercury pollution.

Since his appointment last November, Leavitt has been reexamining the agency's mercury plan, which envisions a 70 percent cut in mercury emissions from coal-burning power plants by 2018, from the current 48 tons a year to 15 tons.

"The final rule will concentrate on the need to protect children and pregnant women," Leavitt said.

Environmental groups oppose the proposed mercury regulations, saying they weaken protections under the Clean Air Act.

Angela Ledford, who directs an environmental advocacy coalition that includes the National Environmental Trust, U.S. Public Interest Research Group and Clean Air Task Force, said the EPA would do better to enforce current rules under the Clean Air Act.

"Nothing has changed," she said. "Instead of strengthening the rule so it reduces more mercury faster, Mike Leavitt is moving forward with a rule that was largely written by industry and is the subject of an EPA inspector general investigation."

New Jersey and other Northeastern states have also been vocal critics of the plan. They say current technology could cut mercury emissions from power plants by 90 percent almost immediately and accuse the Bush administration of going easy on friends in the energy business.

Leavitt said the agency is reviewing the comments, and that a final rule would be issued in mid-March.

Mercury from power plants settles in waterways and accumulates in fish. The toxic metal can cause neurological and developmental problems, particularly in fetuses and young children.

About 8 percent of U.S. women of childbearing age have enough mercury in their blood to put a fetus at risk, according to the EPA.