The top U.S. auto safety regulator said on Thursday he will move quickly to take action in response to Fiat Chrysler Automobiles NV’s (FCHA.MI) (FCAU.N) mishandling of recalls involving up to 11 million vehicles. Mark Rosekind, who heads the National Highway Traffic Safety Administration, said action could come by the end of July and take the form of either a consent agreement with Fiat Chrysler or unilateral enforcement action.