Senators are set to take a last run at producing a climate and energy law tomorrow, betting on the spectre of environmental disaster raised by the BP oil spill to build support for a comprehensive overhaul of America's energy strategy.

But despite a strong push from the Obama administration, there are concerns the debate about the energy future could be lost in the wrangling about offshore oil drilling permits.

The official roll-out by Senators John Kerry and Joe Lieberman caps eight months of negotiations with political figures and industry executives aimed at getting broad support in Congress for shifting the economy away from coal and oil and reducing greenhouse gas emissions. Climate legislation passed by the US Senate could unblock a major obstacle which prevented agreement on a binding global deal at last year's Copenhagen summit.

"We are more encouraged today that we can secure the necessary votes to pass this legislation this year in part because the last weeks have given everyone with a stake in this issue a heightened understanding that as a nation, we can no longer wait to solve this problem which threatens our economy, our security and our environment," Kerry and Lieberman said in a joint statement.

The White House is also trying to use the disaster to make a case for a bill. "This accident, this tragedy, is actually heightening people's interest in energy in this country and in wanting a different energy plan," Carol Browner, the White House climate adviser told Bloomberg television at the weekend.

Time is fast running out for climate and energy legislation, with Democrats expected to suffer heavy losses in the mid-term elections.

But the thinking in Congress is that the economic disaster in the Gulf

is more likely to hurt, than help, such efforts in large part because offshore drilling was a key part of the proposals.

The two Senators deliberately gave a boost to offshore drilling under a strategy that saw the Obama administration and the White House working to build support among Republicans and industries that stood to be affected by the new regulations.

Early drafts promised to build more nuclear power plants and expand offshore oil drilling. The pro-business message was further underlined in plans for a roll-out originally scheduled for last month, which envisaged a public show of support from big oil companies, including BP.

The proposal is expected to require a 17% cut in emissions levels from 2005 levels by 2020. Earlier versions suggested a sector-by-sector approach to emissions cuts. Electricity producers would face a cap in 2012, with heavily polluting industries such as steel and cement manufacturers winning a delay until 2012.

In addition to financial incentives for nuclear power and offshore oil and gas drilling, the proposals would have created funds for carbon capture and storage.

The proposals would also have curbed the powers of the Environmental Protection Agency to acting on emissions, and would have stopped states, such as California, from imposing more stringent environmental regulations.

Such concessions to the nuclear and oil industry, while angering environmentalists, do not appear to have created a solid bank of Republican support.

Kerry and Lieberman lost their lone Republican ally, Lindsey Graham. The South Carolina Senator, who initially withdrew his support over a dispute about immigration, now argues the spill in the Gulf has wrecked any chance of success.

"There are not nearly 60 votes today and I do not see them materialising until we deal with the uncertainty of the immigration debate and the consequences of the oil spill," he said in a statement.

The Senate majority leader, Harry Reid, also cast doubt this week on the likelihood of getting a comprehensive climate and energy bill through the Sentate. He told Spanish language Univision network a limited energy-only bill — that would not cap emissions — stood a better chance.

Meanwhile, the battle lines are being drawn on offshore drilling. Some Democratic Senators are now threatening to vote against any climate bill that allows expanded drilling. "I will have a very hard time ever voting for offshore drilling again," Senator Jay Rockefeller, a West Virginia Democrat told reporters.

Others, including Graham, remain adamant in their support for drilling.

Environmental organisations are also expanding their campaigns against drilling, both in the Gulf of Mexico, and new projects scheduled for Alaska.

That could force yet another revision to the proposal by the time it sees the light of day on Wednesday. "The one part we are still talking about is the offshore drilling," Lieberman told reproters. "The other parts are really in pretty solid shape."