  If a heavy Dirac monopole exists, the light to light scattering below the
monopole production threshold is enhanced due to the strong coupling of
monopoles to photons. This effect could be observable in the collision of
virtual photons at proton colliders. At the Tevatron it will be seen as pair
production of photons with energies 200--400 GeV and roughly compensated
transverse momenta 100--400 GeV/c. This effect could be seen at monopole masses
about 1--2.5 TeV at the upgraded Tevatron and 7.4--19 TeV at LHC depending on
monopole spin.
