A method of reducing access to communication system resources by a fraudulent Mobile Station (102). The Mobile Switching Center (104) sends a message to the Authentication Center (106) to invoke a first authentication procedure. The Authentication Center responds with a message including the results of the first procedure, and possibly, parameters for performance of an additional authentication procedure. Based on the contents of the message, the Mobile Switching Center decides whether to delay call setup until after the additional authentication procedure has completed successfully or whether to initiate call setup in parallel with the additional authentication procedure.