It is computationally expensive to evaluate the overall system level reliability when several interacting failure modes are present. Therefore, it is even more expensive to optimize considering the system level reliability that accounts for the interactions between failure modes. In this paper, we decompose the system level reliability based optimization problem using surrogates into less expensive problems with fixed risk allocation for each failure mode. In addition, the fixed risk allocation problem is transformed from a purely probabilistic problem to a deterministic one through an iterative process of updating safety factors to limit the number of calls to evaluate the reliability. We found that the number of calls to the simulation to evaluate the system level reliability was reduced by 77% with this methodology.