Despite the ever-shrinking legislative window for the 110th Congress, lawmakers will debate a landmark environmental bill later this spring and also are set to back renewable energy tax breaks that expire at the end of the year.

Senate Majority Leader Harry Reid (D-Nev.) has set aside June 2 to begin floor debate on the Lieberman-Warner Climate Security Act (S. 2191), a historic bill that aims to reduce greenhouse gas emissions through an economy-wide cap-and-trade program.

“We have a very strong bill that gets the job done,” Senate Environment and Public Works Chairwoman Barbara Boxer (D-Calif.) said of the legislation this month.

Under the cap-and-trade scheme created by the bill, the government sets limits on annual emission levels and distributes credits that can be bought, traded or sold by companies and other entities. The cap gradually is tightened over time, thereby reducing atmospheric concentrations of greenhouse gases blamed for global warming.

While the bill’s proponents, including Sens. Joe Lieberman (ID-Conn.) and John Warner (R-Va.), are mounting an all-out push to attract the 60 votes necessary for passage, the looming debate largely is seen as an exercise for mapping out a path for enactment by a subsequent Congress and new administration. President Bush opposes cap-and-trade, favoring instead voluntary actions and the development of new technologies for reducing emissions.

Boxer, who will manage the bill on the floor, acknowledged the uphill battle it faces but said the legislative debate needs to get under way.

“We’re going to have to get it started and move it as far as we can get it, because there’s no question the next president is going to support a bill, and we want to see how our votes line up,” she said.

Boxer, Lieberman and Warner are meeting Senators individually to try to win support, in hopes of crafting a centrist bill that will be effective in reducing emissions without causing severe economic effects.

Warner admitted the legislation is a tough sell for many Republican Senators. “I’ve got extra work to do,” he said recently.

Still, the pending floor debate coupled with the support for cap-and-trade by presumptive GOP presidential nominee Sen. John McCain (Ariz.) is prompting Republicans to consider the party’s position on global warming. Diverse opinions were expressed when about 40 GOP Senators met behind closed doors to discuss the issue earlier this month.

In the House, the prospects for a full debate on cap-and-trade appear to be fading. While Speaker Nancy Pelosi (D-Calif.) has elevated the profile of global warming this Congress through the creation of a select committee, she recently admitted it was unclear whether an effective bill would be ready in time for legislative action.

And House Energy and Commerce Chairman John Dingell (D-Mich.) has made it clear that deadlines won’t drive a cap-and-trade bill that his committee is writing. “Though we’re working to complete this process as quickly as possible, we’re most concerned with doing it well,” he said earlier this month.

On a separate energy issue, both the House and Senate are expected to back extending popular renewable energy tax credits that expire at the end of the year. A broad coalition of environmentalists and industry is pressing for a quick extension, citing uncertainty among investors that is hampering an otherwise booming industry.

“Time is of the essence,” said Sen. John Ensign (R-Nev.), who along with Sen. Maria Cantwell (D-Wash.) on April 10 assembled 88 votes in favor of attaching a roughly $6 billion renewable energy extension package to the Senate housing stimulus bill.

Extending the incentives has widespread bipartisan support in both chambers, but previous extension attempts have tripped over offsets. The House wants to pay for renewable incentives by revoking billions of dollars in tax breaks on oil and gas companies, arguing that such relief is unnecessary in light of record industry profits.

But that approach has repeatedly failed to advance in the Senate. The Ensign-Cantwell measure includes no offsets, complicating its passage in the House by violating budget-neutral pay-as-you-go rules.

However, Senate Finance Chairman Max Baucus (D-Mont.) is still considering a fully offset extension, while Pelosi on April 10 indicated the renewable incentives could also move as part of a second economic stimulus package.

Despite the favorable prospects for extension, proponents say it needs to happen fast. “We’re at a critical point here and we need to get it passed,” Ensign said.

In addition, Members in both chambers will use the appropriations process to highlight a laundry list of concerns over energy policies. The provisions are unlikely to make it into final spending bills.

Record high prices for crude oil is attracting support for a Senate proposal to halt the addition of oil to the Strategic Petroleum Reserve until markets stabilize. Lawmakers in both chambers have also signaled interest in revisiting a long-simmering dispute dating from the Clinton administration over billions of dollars of unpaid royalties from offshore oil and gas development.

The Bush administration’s decision to pull the plug on a much-touted “clean coal” power plant in Illinois has been widely criticized, while the Department of Energy’s implementation of a controversial federal loan guarantee program for innovative energy projects is facing close scrutiny from a variety of stakeholders.

In addition, House and Senate Republicans have legislation at the ready to repeal a provision from last year’s energy law that prevents the federal government from buying “alternative” fuels that could exacerbate global warming.