A method and apparatus are disclosed for multiple radio access technology (multiple RAT) access mode operation of a wireless transmit/receive unit (WTRU). The WTRU and network configure the WTRU subscription, the WTRUs service agreement, the roaming status of the WTRU, the selected access point name (APN), the Internet Protocol (IP) flow class, the WTRUs subscriber profile identity, the requested quality of service, or the multi-RAT access mode. Operation of the multi-RAT access mode may be enabled based on at least one of a proximity indication indicating proximity to a supporting cell. The WTRU may send a capability indication to the network for support of multi-RAT access, wherein a multi-RAT access mode is enabled based on the capability indication. A partial handover of the bearer may be performed. In performing handover, a target cell is determined according to a priority rule.