2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/10766A mechanism of ultra-high energy (UHE) cosmic ray acceleration in extragalactic radio sources at the interface between the relativistic jet and the ambient medium is discussed as a supplement to the shock acceleration in `hot spots'. Particles accelerated at the jet side boundary are expected to dominate at highest energies. The spectrum formation near the cut-off energy is modeled using the Monte Carlo particle simulations.TeX, 5 pages + 4 postscript figures; to be published in Proc. ICRR Symposium on Extremely High Energy Cosmic Rays, ed. M. Nagano, TanashiAstrophysicstext