The U.S. Climate Action Partnership, a group of 26 big companies and several environmental organizations, proposed reducing greenhouse gas emissions by 80% from 2005 levels by 2050 through an economy-wide cap-and-trade program.

"It will not be cheap and it will not be easy," said Jim Rogers, chief executive of electricity supplier Duke Energy Corp, the third-largest US consumer of coal.

But Rogers and other CEOs from the group urged Congress to pass a new law this year, saying delays will cost the battered economy more in the long-term.

"Our one fear ... is that many in Congress will look for reasons to postpone action," Rogers told the House Committee on Energy and Commerce.

Obama has called for cutting emissions 80% from 1990 levels by 2050. US greenhouse gas emissions rose about 15% from 1990 to 2005.

The United States is the No. 2 greenhouse gas polluter after China. World leaders hope both countries will participate in talks that will produce a successor to the UN's Kyoto Protocol on global warming by the end of this year.

US Rep. Henry Waxman, the California Democrat who chairs the House panel, said he wants to draft a law by the end of May.

"Our job is to ... end this regulatory limbo and set our nations on a responsible path for reducing climate change and achieving energy independence," Waxman said.

But Rep. Joe Barton of Texas, the ranking Republican, said the US economy cannot bear extra costs and maintained that "the science is not settled" on climate change.

The group proposed emission cuts of up to 20% from 2005 levels by 2020, 42% by 2030 and 80% by 2050.

The phased-in approach will help companies and consumers adjust to new costs, said Charles Holliday, chairman of DuPont Co, at a news conference.

Carbon should be regulated at power plants and refineries to make the system as simple as possible, said David Crane, chief executive of NRG Energy Inc.

Other members of USCAP include General Electric Co, BP America, a unit of BP Plc, ConocoPhillips, Deere and Co, and mining giant Rio Tinto.

Under the plan, the government would give polluters credits over time for the right to emit the gases. The credits also could be traded, with polluters purchasing them from institutions that had cut more emissions than required.

Obama has said carbon credits should be auctioned rather than given away to polluters.

U.S. Sen. Bob Corker of Tennessee, a Republican on the Senate Energy Committee, called the proposal "self-serving" and said the government should not give away credits.

Some environmental groups, including the Union of Concerned Scientists and Environment America, said the blueprint was not tough enough.

The plan also features energy efficiency programs, more nuclear power, and investments in renewable energy and the "clean coal" technology opposed by many environmental groups.