Unhappy with the Senate's moves towards overturning an E.P.A. regulation of mercury (that some view as too lax), President Bush has come out with a veto threat, reports the AP's Jim Abrams.

The White House on Monday defended its anti-pollution policies and threatened to veto a Senate proposal to negate new Environmental Protection Agency rules on limiting mercury emissions from power plants.

Senate Democrats, joined by several Republicans, claim that the EPA rules favor the utility industry while slowing action on a serious public health hazard. A Senate vote to overturn the rules was slated for later Monday.

The White House, in a statement, said it supports efforts to reduce mercury emissions and protect public health based on sound science. It said the Senate resolution "would unnecessarily delay the first-ever reduction of mercury emissions from power plants" and that, if it reaches the president's desk, his senior advisers would recommend that he veto it.

The chances of the bill reaching that stage are not high: passage in the Senate is uncertain and is less probable in the House, where the GOP majority rarely deviates from the White House.

The bill's sponsors, Sens. Patrick Leahy, D-Vt., and Susan Collins, R-Maine, turned to a little-used 1996 law that allows Congress to challenge agency rules with a guaranteed floor vote. The law has been successfully invoked only once, when Congress in 2001 repealed Clinton administration workplace ergonomics regulations.

By repealing the EPA rules finalized last March, the Senate would force the agency to return to the tougher Clean Air Act rules imposed during the Clinton administration that requires the nation's 600 coal-burning power plants to use the best available technology to reduce mercury emissions.

Given the severe environmental damage facing New Orleans in the wake of Hurricane Katrina (oil and chemical refineries spewing out their pollutants across the city and region), it is an interesting contrast that the President would issue such a veto threat at this time.