But the bill's chances of passing the Senate are viewed as slim as its supporters are not expected to muster the 60 votes needed to overcome a certain filibuster threat. Prospects in the House are even less certain.
But both Democrats and Republicans appeared eager to debate global warming and both sides are preparing a string of amendments for later this week -- some to make the legislation stronger, others to weaken it.
GOP senators hope to focus on the potential economic impact of the legislation, predicting the shift away from carbon-intensive fossil fuels like coal and oil will lead to higher costs for electricity, gasoline, natural gas and fuel oil for heating.
Meanwhile Democratic sponsors of the bill are trying to blunt the cost issue by proposing to funnel tens of billions of dollars a year to help people pay their energy bills, ease carbon-intensive industries' transition away from fossil fuels, and spur development of alternative energy sources.
The bill would cap the amount of carbon dioxide that affected industries would be allowed to release. Companies would be provided emission allowances -- some for free and other auctioned off. The allowances could be traded in an open market among companies that either need to buy them to met the emissions cap, or can sell them because their emissions have fallen below the cap.
Revenue from the pollution allowances -- an estimated $6.7 trillion over nearly four decades -- would be used to hold down the cost of complying with the new carbon limits, and help people pay energy bills. Some of the money would be used for $800 billion in tax break over the 40 years for people facing high energy costs, according to the bill's sponsors.
The legislation "will give us the resources to help consumers with energy costs, without increasing the (federal) deficit," said Sen. Barbara Boxer, D-Calif., a key sponsor and chairman of the Environment and Public Works Committee. "This bill provides the tools we need to make America more energy independent by investing in energy efficiency and new clean energy sources."
The bill would require an 18 percent reduction of greenhouse gases below 2005 levels by 2020 and about 70 percent below that level by 2050. Some sources would not be covered, so the overall U.S. emission reductions would be by about two-thirds by 2050.
While environmentalists have preferred even stronger measures that would cut greenhouse emissions by as much as 80 percent by mid-century, most support the Senate bill as a step in addressing climate change. The bill also has picked up support recently from a dozen unions, the nation's mayors, a number of governors and religious groups.
General Electric Co., Alcoa Inc., and Exelon Corp, the country's biggest operator of nuclear power plants, are expected Monday at a news conference with Boxer and Sen. Joe Lieberman, I-Conn., another chief sponsor, to support the legislation.
But many business groups, including the U.S. Chamber of Commerce, have criticized the measure as too costly. The charge against the bill has been lead by those that would be most affected including the oil and coal industries.
Such carbon reductions in the time required by the legislation threatens "the American way of life," declares an advertisement by the American Association for Clean Coal Electricity, whose members include coal companies and utilities that rely heavily on coal.
The bill's supporters counter with studies that show modest cost increases from the emission caps if there is an expansion of alternative energy sources including solar, wind and carbon-free nuclear power as well as energy efficiency and conservation.
"We want to make sure ... we don't forget that the cost of inaction on global warming would be much higher than the cost of the emission reductions called for in this bill," said Daniel Lashoff, director of the Climate Center at the Natural Resources Defense Council.
