The new competitive environment changes the paradigm of power system operation. In the transmission area, open access process provides fair accessibility for all market participants. Congestion management is one of the most important side effects of this new process. This paper proposes a new approach for congestion management which is based on both active and reactive re-dispatch of the network critical buses. The critical buses including both generation and interruptible loads, are determined through a sensitivity analysis. Due to the important effects of the market pricing rules on the congestion cost and its allocation, two types of these rules, namely uniform and pay as bid pricing are investigated in the paper. The numerical results of case studies show the effectiveness of the proposed approach.