WASHINGTON – Volkswagen Chief Executive Officer Matthias Mueller met with the top U.S. environmental official for about an hour on Wednesday, a day after California regulators rejected a plan to fix hundreds of thousands of diesel cars with excess emissions as inadequate and not fast enough.

Mueller met with EPA Administrator Gina McCarthy along with Herbert Diess, head of the company’s VW brand, and left around 11 a.m. ET from the agency’s headquarters without making any comments.

Image: Volkswagen chief executive Matthias Mueller

Image: Volkswagen chief executive Matthias Mueller

“We appreciate the time that Administrator McCarthy took to meet with us,” the company said in a statement. “Volkswagen will continue to fully cooperate.”

The German automaker declined to answer questions about the meeting, which Volkswagen had requested .

“We appreciated the conversation with Volkswagen,” McCarthy said, “We will continue to work toward a solution.”

In Detroit, Chris Grundler, who heads the agency’s Office of Transportation and Air Quality, said at a Automotive News forum that the agency wanted a fix as soon as possible.

“We are in a hurry,” he said but offered no timetable for approving a fix or offering details on why VW’s initial proposal fell short.

On his first U.S. visit since the emissions scandal erupted in September, Mueller has been meeting with government officials in Washington since late Monday.

California Regulators Reject VW Recall Plan to Fix Emissions-Cheating Vehicles

On Tuesday, California air quality regulators rejected Volkswagen’s recall plan to fix the diesel vehicles programmed to trick government emissions tests.

Calling the German automaker’s proposed fix “unacceptable,” the California Air Resources Board said the plan does not meet its standards.