-- The Bush administration has sent its long-awaited plan to slash power plant emissions to Congress, but prospects for its passage are questionable, especially in the Senate. President George W. Bush in February unveiled his so-called "Clear Skies" proposal to cut three harmful power plant emissions by 70 percent by 2018 through a cap-and-trade system to control smog, acid rain and soot.

At the request of the White House, two Republican lawmakers, including Louisiana Rep. Billy Tauzin, introduced the bill in the House of Representatives on Friday. Republican Senator Robert Smith of New Hampshire was set to introduce a companion bill on Monday.

The new measure would "do more to clean up emissions from power plants than ever before," Bush said in a statement on Monday. But it faces a fight from Democrats and environmentalists in the Senate for excluding heat-trapping greenhouse gases.

Sen. Jim Jeffords, a Vermont Independent who chairs the Senate's Environment and Public Works Committee, has introduced a competing measure with more stringent caps than the Bush proposal and a first-ever U.S. limit on carbon dioxide emissions.

Jeffords' legislation, approved by his committee in June, would cut carbon dioxide emissions by 23 percent by 2008. That proposal is unlikely to reach the Senate floor before mid-September, a committee staffer said.

The Bush administration's lack of action on greenhouse gases "is ignoring its own warnings on the devastating effects of global warming," Jeffordssaid in a statement. He referred to a report released by the administration in June that cited human activities as a main cause of global warming. Bush dismissed that report as a product of the "bureaucracy."

Bush last year pulled the United States out of the Kyoto treaty, which would have required it to cut greenhouse gas emissions seven percent below 1990 levels by 2012. Bush said the targets would be too costly for the U.S. economy.

The United States is the world's largest emitter of greenhouse gases such as carbon monoxide and methane, which are produced by automobiles and industrial facilities like power plants.

Affirming the tension between economic and environmental goals, Bush said the measure will use "a market-based system that guarantees results while keeping electricity prices affordable for the American people."

Frank O'Donnell at the Clean Air Trust criticized the Bush plan as "a step backward in cleaning up pollution. It will give polluting industries many more opportunities to evade the law."

Utility lobbyists lauded it as a better starting point for negotiations than the Jeffords plan. "It sets another viewpoint out there, which is needed," said Frank Maisano with the Electric Reliability Coordinating Council. "Obviously this is not a short-term issue."