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