  We study the t-J model with the inclusion of the so called three-site term
which comes out from the t/U --> 0 expansion of the Hubbard model. We find that
this singlet pair hopping term has no qualitative effect on the structure of
the pure mean field phase diagram for nonmagnetic states. In accordance with
experimental data on high-T_c materials and some numerical studies, we also
find wide regions of phase coexistence whenever the coupling J is greater than
a critical value J_c. We show that J_c varies linearly with the temperature T,
going to zero at T=0.
