General Motors has begun work on a mass-produced plug-in hybrid vehicle as part of what the world's biggest carmaker sees as an inexorable shift towards electrically-powered cars and trucks.
"We see a logical journey from stand-alone, largely mechanical automobiles to vehicles that run on electricity," Rick Wagoner, GM's chief executive, said at the Los Angeles auto show last week. Wagoner's remarks come amid growing interest in alternative fuels as a result of the recent rise in oil prices, as well as mounting pressure from environmental groups for action against global warming.
The US Supreme Court began hearing a closely-watched case last Wednesday in which 12 states, backed by environmental groups, are asking that the Environmental Protection Agency be required to set nation-wide limits on carbon dioxide and other greenhouse gases emitted by vehicle exhausts.
The Bush administration and the automotive industry have opposed the claim, partly on the grounds that the Clean Air Act's definition of "air pollutants" does not cover greenhouse gases.
Carmakers plan to unveil numerous fuel-efficiency initiatives at the Los Angeles show.
DaimlerChrysler, Volkswagen and BMW are promoting diesel vehicles that would meet air-quality standards in all US 50 states, including California, which has the strictest rules.
Ford will display a prototype of a hydrogen fuel-cell Explorer sport-utility vehicle that, it says, can travel 350 miles on one tank of hydrogen.
The concept of plug-in hybrids, with more powerful batteries than the conventional hybrid petrol-electric vehicles already on the road, has enjoyed growing attention in recent years. The batteries of plug-in hybrids would typically be recharged at night.
Plug-in supporters estimate fuel costs at half those of conventional hybrids. The vehicles would cut greenhouse gas emissions in half.
A small number of conventional hybrids have been converted to plug-ins, but the cost and weight of the batteries have so far discouraged commercial production.
Mr Wagoner said that GM aimed to mass produce a plug-in hybrid version of the Saturn Vue crossover utility vehicle.
He cautioned that production timing would depend on the development of suitable battery technology: "The technological hurdles are real but we believe they're also surmountable."
GM, Ford and DaimlerChrysler's Chrysler division have also pledged to double production of vehicles capable of running mostly on bio-fuels, notably ethanol, by 2010.
Mr Wagoner announced on Wednesday that GM's gargantuan Hummer sport-utility vehicles will be equipped to run on ethanol within the next three years.
In contrast to the carmakers' enthusiasm, environmental activists plan numerous protests in Los Angeles this week against the industry's slow progress in dampening Americans' thirst for oil.
Mike Hudema of Global Exchange said that "if they're serious about making an environmental commitment, then Ford, GM, Toyota and the rest of the carmakers will commit to mass produce fuel-efficient cars, rather than mass-market environmental dreams."