It's back to the drawing board for Volkswagen in yet another setback for the embattled automaker.

On Tuesday, United States and California regulators rejected the company's proposed fix for the estimated 580,000 vehicles affected in the country by its emissions scandal.

The Environmental Protection Agency and California Air Resources Board (CARB) negated VW's recall blueprint for two-liter diesel cars, with CARB even flagging the automaker for 13 violations, as reported by USA Today.

"The proposed plans contain gaps and lack sufficient detail," CARB said in a joint statement with the EPA on Tuesday, as reported by USA Today. "The descriptions of proposed repairs lack enough information for a technical evaluation; and the proposals do not adequately address overall impacts on vehicle performance, emissions and safety."

The EPA added: "EPA agrees with CARB that Volkswagen has not submitted an approvable recall plan to bring the vehicles into compliance and reduce pollution. EPA has conveyed this to the company previously."

The timing couldn't be any worse, considering VW had yet again apologized to the U.S. during the Consumer Electronics Show (CES) 2016 last week in Las Vegas and its CEO, Matthias Mueller, apologized again Sunday during the launch of the 2016 North American International Auto Show in Detroit.

Mueller is slated to meet with EPA administrator Gina McCarthy in Washington, D.C. on Wednesday to discuss a U.S. fix for VW's emissions scandal.

A glimmer of hope is that VW told USA Today and other media outlets on Tuesday that the rejection of its proposed recall pertains to a repair blueprint submitted to U.S. regulators and CARB in December, and since then, the automaker has had significant conversations with CARB.

U.S. fixes could range from simple software updates to installing new parts altogether. This past December, VW was given the green light to begin making 8.5 million faulty diesel vehicles comply with emissions regulations in Europe — a massive job that the company is aiming to complete by the end of this year.

"Our most important task in 2016 is to win back trust," Mueller told reporters during the Detroit Auto Show earlier this week. "It's not only our cars that we have to fix. We know we have to repair our credibility, too."

VW must do just that in the eyes of the EPA, CARB and definitely the public.