Discussions between California and federal officials regarding vehicle emissions and fuel economy standards have broken down, Bloomberg reports.

California’s Air Resources Board had been meeting with the Environmental Protection Agency (EPA) and National Highway Traffic Safety Administration (NHTSA) to reach a compromise for new fuel efficiency regulations being pursued by President Donald Trump.

A multitude of automakers have been pressuring the Trump administration to ease fuel efficiency standards from the Obama-era. Trump’s Safer Affordable Fuel-Efficient Vehicles Rule stipulates a corporate average fuel economy rating of 37 mph (6.3 lt/100 km) after 2020, a figure well below the 54.5 mpg rating (4.3 lt/100 km) implemented by the Obama administration.

Neither the EPA or NHTSA have commented on the breakdown in discussions. However, California Air Resources Board spokesman Stanley Young confirmed the impasse.

“The administration broke off communications before Christmas and never responded to our suggested areas of compromise — or offered any compromise proposal at all. We concluded at that point that they were never serious about negotiating, and their public comments about California since then seem to underscore that point,” Young said.

Carmakers have urged President Trump to iron out a compromise with California to ensure nationwide uniformity in fuel economy standards.

California, and twelve other states, have said they won’t comply with Trump’s new laws and are sticking with those standards established by the Obama administration. These states account for roughly one-third of all auto sales in the United States.

EPA acting administration Andrew Wheeler briefly met with CARB chairman Mary Nichols earlier this month but both told the media they have vastly different opinions on the rules.