Is rebirth a conventional truth within the Buddha's message?

There is a lot on this site (and elsewhere) on the validity of rebirth, whether it is necessary to understand the Buddha's message, or to reach enlightenment etc. My question is slightly different where within the two truths doctrine is rebirth placed by the Buddha? I understand that 'the two truths' developed a little later on, but in that later developments within Buddhism were and still are heavily influenced by the Buddha's words (Dhamma and Vinaya), is it possible to come to an agreement on whether rebirth deserves to be considered an ultimate or conventional truth? Here's my thought: rebirth is conditioned by death and the workings of Kamma, therefore it seems to fit into conventional truth pretty neatly. It also makes no sense from the ultimate point of view - no conditioned experience can either be affirmed or denied within the ultimate standpoint, so whilst rebirth does not make 'positive sense' from the ultimate stand point, it also can't be denied altogether (that is to say, ultimate truth is empty of rebirth). Is rebirth a concept that cannot be affirmed when considering ultimate truth, but cannot be denied when considering conventional truth? (edit: I assume rebirth occurs and is evident. The fact that 'every thing that has a beginning has an ending' demands rebirth if avoiding annihalationism)