[en] A ratio is derived, which on the one hand summarises causality principle in the local theory, and on the other hand, permits to describe interaction dynamics of quantum-field objects with nonlocal classical sources fully enough. Causality principle for such interaction is formulated. Building scheme of s matrix in the framework of perturbation theory is given for quotient type of nonlocal sources. Ultraviolet divergences appearing are analyzed. It is pointed out, that in supposition of smallness of a nonlocal source approximation to dispersion on local source might be obtained