  We calculate the antiproton flux due to relic neutralino annihilations, in a
two-dimensional diffusion model compatible with stable and radioactive cosmic
ray nuclei. We find that the uncertainty in the primary flux induced by the
propagation parameters alone is about two orders of magnitude at low energies,
and it is mainly determined by the lack of knowledge on the thickness of the
diffusive halo. On the contrary, different dark matter density profiles do not
significantly alter the flux: a NFW distribution produces fluxes which are at
most 20% higher than an isothermal sphere. The most conservative choice for
propagation parameters and dark matter distribution normalization, together
with current data on cosmic antiprotons, cannot lead to any definitive
constraint on the supersymmetric parameter space, neither in a low-energy
effective MSSM, or in a minimal SUGRA scheme. However, if the best choice for
propagation parameters - corresponding to a diffusive halo of L=4 kpc - is
adopted, some supersymmetric configurations with the neutralino mass of about
100 GeV should be considered as excluded. An enhancement flux factor - due for
instance to a clumpy dark halo or to a higher local dark matter density - would
imply a more severe cut on the supersymmetric parameters.
