  We evaluate the possible deviation (from the conventional Cahn's result) of
the phase between the one-photon-exchange and the `nuclear' high energy $pp$
scattering amplitudes in a small $t\to 0$ region caused by a more complicated
(not just $exp(Bt)$) behaviour of the nuclear amplitude. Furthermore we look at
the possible role of the $t$-dependence of the $\rho(t) \equiv$ Real/Imaginary
amplitude ratio. It turns out that both effects are rather small - much smaller
than to have any influence on the experimental accuracy of $\rho(t=0)$
extracted from the elastic proton-proton scattering data.
