A method, apparatus and computer-readable medium for improving push-to-talk call setup speed by disabling an idle mode of a mobile station are provided. According to the method, a deregistration request is received from a mobile station. The base station determines whether a push-to-talk service flow exists for the mobile station, based upon a unique identifier for push-to-talk service flow for the mobile station. If the service flow does exist, then the base station transmits a deregistration command to the mobile station including an action code that instructs the mobile station to disable its idle mode and change its mobility feature supported field to sleep only mode. Since the time required to transition from sleep mode to active mode is less than from idle mode to sleep mode, the push-to-talk call setup speed is improved.