Three powerful lobbying forces — automakers, electric utilities and the coal industry — are confounding Democrats' efforts to forge a less-polluting energy policy.

Disputes over automobile fuel economy, use of coal as a motor fuel, and requirements for utilities to use more wind or biomass to generate electricity have threatened to stall energy legislation in both the Senate and House.

The issues have been the focus of intense lobbying by the coal industry, electric utilities heavily dependent on coal, and by automobile manufacturers trying to block new fuel economy requirements from Washington and in a dozen states.

Unless agreements can be worked out in the coming days, the impasse could dash hopes by Senate Majority Leader Harry Reid and House Speaker Nancy Pelosi to produce an energy bill — the first since Democrats took control of Congress — before Independence Day as promised.

Democrats this week are trying to find a way around a threatened filibuster and resurrect a proposal to require electric utilities to use more renewable fuels and spur development of wind, solar and biomass energy sources.

An intense GOP fight against the proposal has been waged largely at the behest of two of the country's biggest coal-burning electricity producers — the Atlanta-based Southern Company and the Tennessee Valley Authority. The companies, in letters to senators, argue that the requirement to produce 15 percent of their power from renewable energy sources can't be met without huge electricity cost increases. Supporters of the measure argue that is false.

The coal industry has weighed in as well, urging support of an alternative that would have included more efficient coal-burning power plants and nuclear reactors eligible under the mandate, a plan senators rejected.

Bill Wicker, a spokesman for Sen. Jeff Bingaman, D.N.M., the lead sponsor of the renewable fuels mandate, said the senator views promotion of renewable fuels a core ingredient of a fresh energy policy and if the GOP continues to block a vote it could "unplug the whole bill."

Meanwhile, another imbroglio that threatens to derail Senate action on energy — and also has complicated progress on energy legislation in the House — centers on demands that automakers significantly improve the fuel efficiency of their vehicles.

The automakers have unleashed an intense campaign to block a requirement already in the Senate bill that calls for new cars, SUVs and small trucks to meet an average fuel efficiency of 35 miles per gallon by 2020 with further annual improvements of 4 percent after that.

Dozens of car dealers and auto plant managers were making the rounds of Senate offices to lobby against the measure this week. Chief executives of the Big Three automakers recently came to Capitol Hill to tell Senate leaders the proposed requirement can't be met. Auto industry lobbyists said it would mean fuel economy would have to more than double by 2030 to a fleet average of 52 mpg.

Sen. Carl Levin, D-Mich., brandishing a letter from the auto manufacturers' lobbying group outlining its opposition to the Senate provision, plans to join several other senators close to the auto industry and offer a more modest proposal, possibly as early as Tuesday.

Automobile and coal interests also have played havoc with Democrats' plans for energy legislation in the House.

Pelosi, who has promised an energy bill before Independence Day, has been at loggerheads with Rep. John Dingell, D-Mich., chairman of the Energy and Commerce Committee and a longtime protector of the automakers, over a package of energy proposals being crafted by Dingell's committee.

A focus of Pelosi's ire, is a provision that Dingell engineered into the bill that would not only bar the Environmental Protection Agency from regulating "greenhouse" gas emissions from automobiles, but block California and 11 other states from doing so.

The auto industry has been fighting the California mandate, which cannot go into effect unless the federal EPA gives a green light.

Pelosi and key Democrats on Dingell's committee also have been at odds over another provision in the draft bill — one of intense interest to the coal industry — that is aimed at promoting liquefied coal as a motor fuel.

Rep. Rick Boucher, D-Va., whose district is in the heart of coal mining country, included in a draft energy bill an array of incentives and mandates to promote development of liquefied coal as an alternative to diesel and jet fuel.

Such government help has been a top priority for the coal industry. "It's very important. It opens an entirely new market for coal," said Luke Popovich, a spokesman for the National Mining Association, which represents coal interests in Washington.

Coal companies argue coal is America's most abundant energy resource and can replace imported oil. But environmentalists worry that processing coal into a liquid fuel will produce more carbon dioxide and add to the problem of global warming. The issue has strong Republican support and has divided Democrats in both the House and Senate, where a similar liquid coal provision is expected to be offered.

Pelosi, who has made addressing global warming a priority, opposes Boucher's provisions. In the Senate, among those pushing for more liquefied coal development is Sen. Barack Obama, D-Ill., who represents a state also with significant coal interests.

Both Boucher and Obama have said their provisions would require that the liquid coal produce no more greenhouse gases than the use of conventional gasoline. Still, that has not satisfied environmentalists who view development of such a fuel as a step back in dealing with climate change.