A first wireless device transmits a first sidelink transmission via a first resource, where the first sidelink transmission includes a field indicating resource reservation of a second resource for a second sidelink transmission by the first wireless device. Based on an absence of an acknowledgement (ACK) corresponding to the first sidelink transmission, the first wireless device determines to use the second resource to receive inter user equipment (inter-UE) coordination information from a second wireless device. The first wireless device receives, from the second wireless device and based on the determining, the inter-UE coordination information indicating a set of third resources for one or more third sidelink transmissions by the first wireless device.