In this paper, a method of inter-area routing in a telecommunications network based on the principles of Traffic Engineering is proposed. The method is based on a diakoptical approach that involves splitting a general routing problem into several routing over areas subtasks of lower dimensionality and complexity and then obtaining a generalized solution based on combining solutions obtained in individual areas. The application of the proposed method is focused on improvement of the scalability of routing solutions without losing their efficiency, which is evaluated by the upper threshold of network link utilization.