The European Union, Japan and much of the rest of the industrial world are imposing mandatory cuts on emissions linked to global warming. The Bush administration favors asking US companies to join a voluntary emission reduction program.

Sen. Pete Domenici, who chairs the Senate's energy committee, believes the United States should take a tougher stand. Domenici and his Democratic colleague on the panel, Sen. Jeff Bingaman, jointly issued the "white paper."

Alex Flint, Republican staff director for the energy panel, said any climate change legislation is "months away" and such a bill "is dependent on whether a consensus can be reached" on how to deal with global warming.

The paper seeks answers to several key questions, including whether the entire US economy or just certain sectors should be regulated in any greenhouse gas program.

The paper notes that no single sector of the US economy, such as transportation or industry, makes an overwhelming contribution to America's total greenhouse gas emissions.

"If a key design feature is fairness, then no one sector should be singled out," the paper says. "An economy-wide approach also allows for ease in seeking the least-cost path to (emission) reductions through trading systems."

The paper also asked how to allocate emission-reduction credits among industry sectors, like coal-burning utilities and oil refineries.

In a briefing with reporters on Capitol Hill, Flint said the public will be asked to comment on issues raised by the paper and the committee will hold a conference in March to hear from climate change experts and industry representatives.

Domenici and Bingaman eventually hope to incorporate the suggestions into legislation. Climate legislation already faces strong opposition from other senators, a large chunk of the House of Representatives and President George W. Bush, who opposes mandatory emissions cuts for US companies.

Senior staff did not think a bill would get very far this year, but would lay the groundwork for action in a future Congress. Bob Simon, the energy committee's Democratic staff director, said it would be "difficult" to get the legislation through Congress this year.

Flint said the "ground is shifting" among lawmakers to deal with climate change. But he would not predict whether a climate change bill could make it to the president's desk this year.