  In this report diffractive high energy reactions are discussed in a
functional integral approach where hadronic amplitudes are calculated from
vacuum expectation values of lightlike Wegner-Wilson loops. In the first part
we calculate elastic differential cross sections for high energy and small
momentum transfer elastic proton-proton (pp) scattering which are in reasonable
agreement with the experimental data. In the second part we consider exclusive
$\pi^0$ production in ep-scattering. At high energies photon and odderon
exchange contribute to this reaction. We show that odderon exchange leads to a
much larger inelastic than elastic $\pi^0$ production cross section, dominating
the $\gamma$ contribution by orders of magnitude. Observing our process at HERA
would establish the soft odderon.
