WASHINGTON (Reuters) - Nearly two dozen U.S. state governors, including those of California and New York, urged the Trump administration on Tuesday to abandon a proposal to freeze fuel-efficiency standards at 2020 levels through 2026.

U.S. President Donald Trump talks with attendees as he departs an event held to tout his administration's environmental policies in the East Room of the White House in Washington, U.S., July 8, 2019. REUTERS/Carlos Barria

The list of 23 states and Puerto Rico includes key 2020 election battlegrounds such as Pennsylvania and Wisconsin.

In August 2018, the administration proposed freezing fuel efficiency requirements and stripping California of the right to set its own vehicle-emissions rules.

The governors, representing 52% of the U.S. population and 57% of the economy, said they want “continuous, meaningful annual reductions in greenhouse gas emissions and criteria pollutants while saving consumers money,” and that they “support preserving state authority to protect our residents from vehicle pollution.”

Environmental Protection Agency chief Andrew Wheeler told reporters on Monday the agency “will be coming out later this summer with our (fuel efficiency) standards, which will also further reduce CO2.”

The Alliance of Automobile Manufacturers, a trade group representing General Motors Co, Volkswagen AG VOWG_p.DE, Toyota Motor Corp and others, said on Tuesday: "It is untenable to face a marketplace with different standards in different states, but it is also untenable to face standards that rise so high that only a handful of electric cars can achieve them."

The group again said it was “urging the federal government and states to find a middle ground that raises standards year over year while aligning with market demand.”

The final regulation faces a multi-year legal battle that could leave automakers in limbo about future emissions and fuel-efficiency requirements.

The Trump administration plan aims to roll back emission standards set by former President Barack Obama.

The Obama-era rules called for a fleetwide fuel-efficiency average of 46.7 miles per gallon by 2026, compared with 37 mpg under the Trump administration’s preferred option.

Last month, 17 major automakers urged a compromise “midway” between the Obama-era standards that require annual decreases of about 5% in emissions and the Trump administration’s proposal.

Reuters reported in April that officials expect the final rule will include a small increase in yearly fuel-efficiency requirements.

Senator Tom Carper, a Democrat, said since the White House had shown no interest in new talks that “automakers should make clear that they will not support this rollback by working directly with California and these 23 states.”

Automakers and government officials say they do not expect EPA and the Transportation Department to finalize the rules before September.