  The ultra--high energy cosmic rays recently detected by several air shower
experiments could have an extragalactic origin. In this case, the nearest
active galaxy Centaurus A might be the source of the most energetic particles
ever detected on Earth. We have used recent radio observations in order to
estimate the arrival energy of the protons accelerated by strong shock fronts
in the outer parts of this southern radio source. We expect detections
corresponding to particles with energies up to $\sim 2.2 \times 10^{21}$ eV and
an arrival direction of ($l \approx 310^{\circ}$, $b \approx 20^{\circ}$) in
galactic coordinates. The future Southern Hemisphere Pierre Auger Observatory
might provide a decisive test for extragalactic models of the origin of the
ultra--high energy cosmic rays.
