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This work proposes a new method for choosing the best transmission system expansion plan for the highest satisfaction level of the decision maker. The proposed method considers the permissibility and ambiguity of the investment budget (economics) for constructing new transmission lines and the delivery marginal rate (reliability criterion) of the system. This is achieved by modeling the transmission expansion problem as a fuzzy integer programming one. The method solves for the optimal strategy (a reasonable and flexible plan that would not be significantly worsened by any assumed changes in the surrounding situations) using a fuzzy set theory-based branch and bound method that utilizes a network flow approach and the maximum flow-minimum cut set theorem. When only a very limited size database is available to evaluate probabilistic reliability indices, the proposed technique provides the decision maker with a valuable and practical tool to solve the transmission expansion problem, considering problem uncertainties. Test results on an existing 21-bus system show that the proposed method is suitable for solving the transmission expansion planning problem subject to practical ambiguities.