Techniques for supporting fallback operation in a multi-carrier communication system are described. In one aspect, a UE may determine at least one first downlink control information (DCI) format to monitor on a first carrier. The UE may monitor for the first DCI format(s) on the first carrier to detect DCI sent to the UE. The UE may receive a reconfiguration message related to communication on a plurality of carriers by the UE with cross-carrier signaling, and may determine at least one second DCI format to monitor on the first carrier based on the reconfiguration message. The UE may monitor for the first DCI format(s) and the second DCI format(s) on the first carrier after receiving the reconfiguration message.