Wireless communications systems and methods related to on-demand ultra-reliable, low-latency communication (URLLC) are provided. In one embodiment, a base station (BS) receives, from a user equipment (UE) in a first cell frequency, a request for a protocol data unit (PDU) session over a network slice. The BS receives, from a core network entity, a resource configuration request for the PDU session over the network slice. The BS transmits, to the core network entity, a resource configuration response indicating a cause for rejecting the resource configuration request. In one embodiment, a UE transmits, in a first cell frequency of a network, a network registration request message requesting a network slice of the network that is not provided by the first cell frequency. The UE receives a network registration response message indicating the network slice is allowed based on a second cell frequency of the network providing the network slice requested.