"It is regrettable that some states have decided to seek environmental claims now, notwithstanding their prior support of this ongoing federal-state collaborative process," the German carmaker said in a statement.

Volkswagen (VW) has sought a comprehensive national resolution in the United States of all environmental issues arising from its emissions test cheating scandal.

As part of these efforts, VW has agreed to buy back or modify affected vehicles, create a $2.7-billion environmental trust and invest $2 billion on infrastructure for zero-emission vehicles.

On Thursday, the Washington Department of Ecology said it had fined VW $176 million for installing illegal software on many of its diesel vehicles to cheat and falsify emissions tests.

VW has 30 days to appeal the penalty to the Washington Pollution Control Hearings Board. It has not said whether it will launch an appeal.

VW's "dieselgate" scandal erupted in September, after the U.S. Environmental Protection Agency said the carmaker had violated the Federal Clean Air Act, forcing the carmaker into a $14.7 billion settlement.

(Reporting by Edward Taylor and Ilona Wissenbach; Editing by Mark Potter)