The invention is a method and apparatus for signaling uplink control information in a mobile communication network using carrier aggregation. The signaling mechanism allows the transmission, on a single uplink component carrier, of control information associated with a downlink transmission on multiple aggregated downlink component carriers. Semi-statically reserved resources for the transmission of control information on the uplink component carrier may be dynamically shared by user terminals that are assigned multiple downlink component carriers for downlink transmissions. Implicit or explicit resource indication can be used in combination with dynamic resource indication.