The Trump administration has ended talks with California aimed at settling their differences over increasing fuel economy and tightening emissions regulations, Reuters reported Thursday, citing an unnamed government official.

In August, the EPA, led by Acting Administrator Andrew Wheeler, released a proposal to freeze emissions and associated fuel economy regulations at 2020 levels through 2026 and revoke California's unique right to set its own emissions standards.

California has sued the EPA, and is now joined by 19 other states in the suit, most of which have signed on to follow its emissions standards. The state insists it will not abide by any new federal standards.

Since then, Wheeler and California Air Resources Board Chairwoman Mary Nichols have held numerous talks aimed at settling the dispute. Ahead of the last round of talks, though, Wheeler told Bloomberg that "in the end, this is not a two-way negotiation."

MUST READ: Analysis: Wheeler says electric cars "not grounds for concern" at the EPA. Really?

As any negotiating expert might say, it is hard to reach an "agreement" if either party is intransigent. The talks have been held privately, so it's impossible to say with certainty how they have gone, but this report, along with Wheeler's comments earlier this month, give a good indication that they have not been fruitful.

Wheeler also said in January that the EPA plans to finalize its ruling on emissions and fuel economy regulations by April.

Increasing Corporate Average Fuel Economy regulations, and incorporating limits on greenhouse-gas emissions (which require higher fuel economy) into those emissions regulations, was one of President Obama's signature environmental legacies, implemented within months of taking office in 2009, along with later limits on emissions from coal-fired powerplants.

DON'T MISS: California warns it won't follow lower EPA fuel economy, emissions rules

The regulations stepped up fuel economy for the first time in 22 years, starting in 2012 and running through the 2025 model year and forced automakers to apply fuel-saving technology to their profitable light trucks as well as to small cars. Obama made the EPA work with the NHTSA (which has statutory authority over fuel economy standards), and California to coordinate emissions and fuel economy standards across all states. 

California has also threatened to sue to maintain its own standards.

The Trump administration has attempted to reverse those Obama achievements by freezing the fuel economy increases, removing California's authority, and loosening emissions standards on powerplants which provide energy for electric cars.

READ THIS: Trump administration releases proposal to weaken fuel economy, emissions standards

As soon as Trump was elected, Detroit automakers lobbied him to loosen the standards, implement a single national policy, and "provide certainty" about the regulations, despite the Obama agreement that put the two agencies and sets of states all on roughly the same page.

With that agreement unraveling, it looks likely to result in a protracted disagreement between the EPA and California and years of lawsuits with uncertain outcomes.