  Cosmic rays with energies exceeding $10^{20}\eV$ have been detected. The
origin of these highest energy cosmic rays remains unknown. Established
astrophysical acceleration mechanisms encounter severe difficulties in
accelerating particles to these energies. Alternative scenarios where these
particles are created by the decay of cosmic topological defects have been
suggested in literature. In this paper we study the possibility of producing
the highest energy cosmic rays through a process that involves formation of
metastable magnetic monopole-antimonopole bound states and their subsequent
collapse. The annihilation of the heavy monopole-antimonopole pairs
constituting the monopolonia can produce energetic nucleons, gamma rays and
neutrinos whose expected flux we estimate and discuss in relation to
experimental data so far available. The monopoles we consider are the ones that
could be produced in the early universe during a phase transition at the grand
unification energy scale. We find that observable cosmic ray fluxes can be
produced with monopole abundances compatible with present bounds.
