Two Democratic senators have effectively blocked President Bush's nominee for chief enforcement officer at the Environmental Protection Agency out of fear the administration won't pursue lawsuits against polluting businesses.

U.S. Sens. Charles Schumer, D-N.Y., and Barbara Boxer, D-Calif., placed a hold Monday on the nomination of Donald Schregardus, keeping the appointment from being voted on by the full Senate.

Schumer said he would not release the nomination until the Republican administration clarifies its role in pending lawsuits against power plants and explains its plan to improve air quality in the Northeast.

For eight years, Schregardus directed the Ohio Environmental Protection Agency after serving in the federal EPA during the administration of Bush's father.

The Senate Environment and Public Works Committee approved his nomination Aug. 1 over the objections of the four Democrats on the committee.

Schumer said Schregardus isn't supportive of the federal role in the acid rain lawsuits and said the nominee supported a 1996 Ohio law that grants immunity from civil action when utility companies voluntarily report violations of environmental regulations.

Environmentalists fear the Bush administration is considering a withdrawal from air pollution lawsuits in which Northeastern states seek to stop polluters in the Midwest and South from contributing to acid rain.

"Pursuing lawsuits against power plants who are skirting clean air regulations is a vital step in protecting air quality standards that affect the health and lives of tens of millions of people," Schumer said.

The White House said Schregardus is a qualified administrator whose nomination shouldn't be held up by the actions of two lawmakers.

"Confirmation should be based upon the qualifications of the nominee, not the narrow agenda of two members of the Senate," Anne Womack, a White House spokeswoman, told The New York Times in Tuesday's editions. "Donald Schregardus is highly experienced and more than qualified."