California environmental officials on Tuesday rejected Volkswagen AG’s proposals for recalling nearly 500,000 two-liter diesel-powered cars, dealing another setback to the German automaker as it tries to clean up the aftermath of the emissions cheating scandal.

The Environmental Protection Agency and California Air Resources Board (CARB), which jointly exposed the Volkswagen violations, said independently that they had rejected the automaker’s recall proposal for 2-liter diesel cars.

The move comes a day before Volkswagen CEO Matthias Mueller is set to meet with EPA administrator Gina McCarthy in Washington, D.C., to discuss the potential fix.

Listing its complaint against VW, CARB said the company violated 13 specific state environmental regulations. It said Volkswagen’s planned technical fix for its two-liter engines was too vague to allow a technical evaluation of the fix.

VW’s proposals also failed to address how the fix would affect the engine’s performance, emissions and vehicle safety, according to CARB. Some experts are concerned that a fix that strengthens the vehicle’s emissions control could reduce fuel economy and overall performance.

The rejection does not eliminate the possibility of the embattled automaker working out a deal with regulators.