Four-Fermi Effective Operators at e^+ e^- ---> \bar{t} t

The process of top quark pair production at Next Linear Collider (NLC) has been considered adopting an effective Lagrangian approach and including all operators of dim~6 which can be tree-level-generated within unknown underlying theory. All contributing helicity amplitudes are presented. It has been found that four-fermion operators can provide the leading non-standard contribution to the total cross section. Expected statistical significance of the non-standard signal for the total cross section and forward-backward asymmetry have been calculated taking into account existing experimental constraints. It has been shown that adopting realistic luminosity of NLC and conservative efficiency for the top-quark pair detection, the total cross section may be sensitive to non-standard physics of an energy scale around $\Lambda=5\tev$.