Methods and apparatus are provided to reduce service interruption for intra-RAT and inter-RAT handover procedures. The UE performs a NAS signaling procedure via a NAS signaling connection in a mobile communication network. The UE monitors a radio resource status and determines whether a radio bearer has been or is being established for a RRC connection for data transmission. The UE determines whether to release the NAS signaling connection after completing the NAS signaling procedure based on whether the radio bearer has been established. In one embodiment, the UE monitors a radio resource status and determines whether a radio bearer has been established for a RRC connection for data transmission. The UE determines whether to start a timer upon completing the NAS signaling procedure based on whether the radio bearer has been or is being established.