On Thursday, 17 automakers sent the White House a letter asking the Trump Administration to put the brakes on a fuel economy rollback, according to the New York Times.

Automakers including Ford, General Motors, Toyota, and Volvo reportedly asked the Trump Administration to go back to the negotiating table with California and a dozen other states following California's lead in imposing fuel economy standards that were agreed upon during the Obama Administration.

In December 2016, the Obama-era Environmental Protection Agency finalized a set of fuel economy standards that would require automakers to meet a target of 54.5 miles per gallon by 2025. When the Trump Administration took over, it set in motion the process to make those fuel economy standards less stringent—after considerable lobbying from the automotive industry. Last summer, the EPA finally proposed a fuel economy rollback that would freeze target miles-per-gallon at 2020 levels, ignoring the Obama Administration's final five years of increasingly stringent standards.

The Trump EPA's proposed rule also moved to revoke a waiver that was granted to California decades ago, which allows the state to set its own fuel economy standards. But California officials have said they will fight the EPA, and in April the state sued the EPA and the National Highway Safety Administration (NHTSA) for access to the data that the federal government used to justify the standards rollback. Prominent economists and researchers have criticized the federal government's justification of its rollback, saying it would make the US worse off.

California has promised to continue to enforce the Obama-era fuel economy standards that the state originally agreed to, whether or not the EPA continues with its rollback. More than a dozen other states have also said they would join California in enforcing the Obama-era rules.

The situation creates a problem for the automotive industry, which now faces a bifurcated US market until the federal government can definitively revoke California's fuel economy waiver. Because of this, automakers are now warning the Trump Administration that “an extended period of litigation and instability” will disrupt their industry, according to the letter seen by the Times.