An elastic infinite plane with a circular inclusion at specified tractions and displacements jumps along the interface and under nonzero conditions at infinity is considered. Explicit expressions are derived for Goursat-Kolosov's complex potentials of this problem. The solution constructed can be used for the cases of different circular interfacial defects including interfacial cracks and rigid parts of the interface. It is pointed out that the problem is a base of a superposition method applied to solving a lot of problems in which a circular region is an element of polyphase elastic medium. In such a case, a correctness of the problem statement related with an actual dependance of traction jumps upon displacements jumps and vice versa entirely follows from the superposition method. The technique of the application of this method is demonstrated in this paper by the example of solving singular problems on action of a point force and an edge dislocation located in the inclusion or in the matrix. Computational