The Obama administration is pressing for a new law that would establish a cap-and-trade system to curb emissions from power plants and scores of other sources.
But the administration has also warned that it plans to move ahead with EPA rules absent a final bill. Sen. Lindsey Graham (R-S.C.) is urging GOP colleagues to back an emissions bill in part because Congress, not EPA, should decide the contours of a national emissions program.
The so-called endangerment finding stems from a major 2007 Supreme Court decision that enables EPA to limit the emissions if it finds that greenhouses gases are indeed a danger. The agency issued a preliminary finding in April.
The EPA announcement could also give U.S. negotiators more leverage at the international climate talks in Copenhagen that begin today, demonstrating domestic action even though Congress has not completed a final bill to curb emissions.