  A new generation of upcoming space-based experiments will soon start to probe
the spectrum of cosmic ray antiparticles with an unprecedented accuracy and, in
particular, will open up a window to energies much higher than those accessible
so far. It is thus timely to carefully investigate the expected antiparticle
fluxes at high energies. Here, we perform such an analysis for the case of
antiprotons. We consider both standard sources as the collision of other cosmic
rays with interstellar matter, as well as exotic contributions from dark matter
annihilations in the galactic halo. Up to energies well above 100 GeV, we find
that the background flux in antiprotons is almost uniquely determined by the
existing low-energy data on various cosmic ray species; for even higher
energies, however, the uncertainties in the parameters of the underlying
propagation model eventually become significant. We also show that if the dark
matter is composed of particles with masses at the TeV scale, which is
naturally expected in extra-dimensional models as well as in certain parameter
regions of supersymmetric models, the annihilation flux can become comparable
to - or even dominate - the antiproton background at the high energies
considered here.
