The paper is proposed a new method for voltage stability assessment. The method is adopted to transfer capability between two interconnected area. Traditionally maximum loading condition between two area according to voltage stability is calculated using continuation power flow. In case of complex interconnected structure of power system main disadvantage of continuation power flow is needed to select changes in the power of nodes. The proposed method belongs to the class of direct methods for searching point of collapse. The method is based on optimization procedure. The objective function directly uses the power flow through connections between interconnected area. Specific features are the direct use Jacobi matrix singular condition and flow model. Direct use Jacobi matrix singular condition eliminates eigenvalue analysis and other indirect estimation methods. Flow model is used to solve the problem of poor convergence of optimization procedure. The proposed method was tested on a 7-bus system and showed its effectiveness compared to continuation power flow. © 2023 IEEE.