The Obama administration wants cars and light trucks in the United States to average 56.2 miles per gallon of gasoline by 2025, a standard that will cut the nation’s oil consumption and carbon output significantly while also raising each vehicle’s cost by about $2,375.

The White House’s ambitious opening bid, which it revealed in conversations with domestic auto companies and lawmakers last week, has already sparked resistance. U.S. automakers have offered to raise fuel efficiency over the next eight years to between 42.6 and 46.7 mpg, according to sources who had been briefed on the negotiations.

That would represent an annual fuel efficiency improvement of between 2 and 3 percent compared with the administration’s 5 percent proposal.

In response to a request for comment, White House spokesman Clark Stevens wrote in an e-mail, “We continue to work closely with a broad range of stakeholders to develop an important standard that will save families money and keep the jobs of the future here. A final decision has not been made, and as we have made clear we plan to propose that standard in September.”

The administration has been holding closed-door consultations for weeks on how to set greenhouse gas emission standards for cars and light trucks made for the 2017-25 model years, which would tighten rules finalized in 2010. At this point, passenger cars average 30.2 mpg and light trucks average 24.1 mpg.

Shortly after taking office, President Obama brokered a deal between automakers, state officials who were pursuing their own greenhouse gas emission standards for vehicles, and union officials. Under that agreement, cars and light trucks must average 34.1 mpg by 2016, producing greenhouse gases that are the equivalent of 250 grams of carbon dioxide emitted per mile.

But the next round of negotiations has proven far more contentious, with environmentalists calling for a rule that would translate to at least 60 mpg and automakers saying they cannot achieve that level of efficiency at a price American consumers are willing to pay.

The current White House proposal, first reported Saturday by the Detroit News, is much more demanding than what U.S. car companies say is feasible. The administration could still include several provisions to lessen the rule’s impact, by giving automakers credit for producing flex-fuel vehicles and using refrigerants that emit fewer greenhouse gases.

Roland Hwang, transportation program director for the Natural Resources Defense Council, said he was “cautiously optimistic” about the 56.2 mpg proposal but added, “The devil is in the details for us.”

Noting that the federal government had provided the U.S. auto industry with more than $89 billion in bailout and retooling loans in recent years, Hwang said he was “overwhelmingly disappointed with the automakers for putting such low numbers on the table. That’s extraordinary when you consider how much money we’ve provided them to build fuel-efficient cars. And now they say, ‘You can’t have them.’ ”

Depending on how the rule is crafted, the stricter requirement could save 4.7 billion barrels of oil by 2030 and $705 billion in fuel costs during the same period.

Auto company representatives would not comment Saturday about their specific negotiating position. But in an earlier e-mail, Alliance of Automobile Manufacturers spokeswoman Gloria Berquist said environmentalists have an overly optimistic view of Americans’ commitment to buying fuel-efficient vehicles.

The industry’s message to the White House “is that we need to preserve affordability, vehicle choice, jobs and safety as we improve fuel economy,” Berquist said, noting that a pickup truck outsold all 30 hybrids on the U.S. market combined in 2010.

In an e-mail, Ford spokeswoman Christin Baker wrote: “Ford is proud to continue offering our customers the very best fuel economy and supports increasing fuel economy requirements with one national program that is data driven and factors in the impact of this rule-making on jobs, the economy, consumers and safety.”

In an interview last week, David Vieau, chief executive of battery maker A123 Systems, said he understood why some chafed at the idea of more stringent fuel efficiency rules.

“Nobody in business wants someone putting a regulation on them. You don’t want someone saying, ‘You must do this in a specific period of time and to this point,’ ” Vieau said.