17 major car manufacturers came together to ask US President Donald Trump to hold back on his plan to lower emissions standards in the US.

According to the New York Times and Reuters, the 17 companies co-signed a letter to the President suggesting that his plan is “untenable.”

The Trump administration has long been pushing for a reduction to emissions standards, and it may come as a surprise that many car companies aren’t on board. In fact, major car manufacturers have now made their position on the matter very clear. The car manufacturers are joining the state of California in a fight against reductions to emissions standards. California has been leading 17 other states in a lawsuit against the Environmental Protection Agency (EPA) over planned rollbacks to Obama-era emissions standards. The Environmental Protection Agency, for their part, believes that the standards set under the Obama administration were “not appropriate,” and they would like to see them revised.

A big part of this current dilemma stems from the fact that the US, unlike most other countries with emissions standards, doesn’t have uniform standards nationwide. California, for example, has more stringent regulations surrounding emissions than most other states. Because California is now taking on the EPA, car-makers are worried that the US will end up having two extremely different sets of regulations for emissions. The same car manufacturers that penned the letter to President Trump also sent a letter to California Governor Gavin Newsom. The car manufacturers are allegedly pushing for a nationwide compromise that is “supported by all parties including California” and would ideally meet Obama-era regulations and Trump’s proposal somewhere in the middle. When reached for comment, Governor Gavin Newsom applauded the car manufactures for their efforts, but reiterated that “A rollback of auto emissions standards is bad for the climate and bad for the economy.” He went on to explain that he agrees the US needs a nationwide standard, but one that “doesn’t backtrack on the progress states like California have made.” The White House rejected the appeal and plans to push forward with the plan to reduce emissions standards. “We are moving forward to finalize a rule with the goal of promoting safer, cleaner, and more affordable vehicles,” said White House Deputy Press Secretary Judd Deere, arguing that California’s regulators have not proposed a “productive alternative.”