The California Air Resources Board is rejecting a Volkswagen plan to recall certain diesel passenger cars, calling the proposal incomplete and deficient.

The German automaker has agreed to spend up to $15.3 billion to settle consumer lawsuits and government allegations that its diesel cars cheated on U.S. emissions tests.

But California said Wednesday that Volkswagen hasn’t provided a full description of all defeat devices, and its proposed plan doesn’t let CARB fully evaluate whether it would even fix the emissions.

The California regulator will continue talks with Volkswagen and the Environmental Protection Agency to reach a solution that “fully mitigates the excess emissions.”

An EPA spokesperson said that the agency is working closely with CARB and agrees with California that “VW has not presented an approvable proposed recall plan for the 3.0-liter diesel vehicles.”

A Volkswagen representative called the announcement a “procedural step under California state law,” and said the automaker will continue to work closely with the EPA and CARB to reach a solution “as quickly as possible.”