This paper addresses the problem of controlling the performance of optical burst switching (OBS) networks in presence of non-stationary traffic demands. We propose a joint burst admission control and forwarding mechanism that operates in core nodes. This mechanism dynamically adapts its behaviour according to the feedback messages received from other nodes. By not forwarding certain bursts not complying with given requirements, an admission control is implicitly made. Moreover, by forwarding bursts to appropriately selected nodes, traffic balancing is achieved. The advantageous effects of the proposed mechanism can additionally be amplified by granting extra offset time to the burst. The benefits provided by this mechanism are supported by numerical results.