A user equipment (UE) and a Secure User Plane Location (SUPL) Location Platform (SLP) support a SUPL positioning session for at least one uplink or uplink-downlink position method, such as uplink Angle of Arrival or multi-Round Trip Time. To support SUPL positioning for uplink or uplink-downlink position methods, the UE provides an identifier for a serving Access and Mobility Management Function (AMF) and an identifier for the UE to the SLP in a SUPL message. The SLP may exchange positioning messages with a serving base station for the UE using the identifier for the serving AMF and the identifier for the UE. The exchange of positioning messages may enable the SLP to request the serving base station to instigate transmission of uplink positioning reference signals by the UE which may be a key enabler for an uplink or uplink-downlink position method.