  A possibility of tuning the phase of the third-order Kerr-type nonlinear
susceptibility in a system consisting of two interacting metal nanospheres and
a nonlinearly polarizable molecule is investigated theoretically and
numerically. It is shown that by varying the relative inter-sphere separation,
it is possible to tune the phase of the effective nonlinear susceptibility
\chi^{(3)}(\omega;\omega,\omega,-\omega)$ in the whole range from 0 to $2\pi$.
