Developers of safety critical software are becoming increasingly interested in using the agile methods. If an agile approach successfully applied in safety critical applications, it must show that the resulting software system is sufficiently safe to operate. This paper describes an approach which tries to address such needs. It identifies a need for a systematic, iterative method. The proposed approach uses the concept of safety modular decomposition to carry out the safety process in the system and safety backlog to manage the safety requirements. An analysis process, which can be used to generate better solution through the iterations, is described. The use of this approach to construct a safety argument is demonstrated. The approach has promised results and could lead to an acceptably safe system developed by using the Adaptive Software Development model (ASD).