Interaction of a fluxon with an rf radiation emitted into a long Josephson junction is investigated analytically and numerically. We use a model based on the sine-Gordon equation driven by a periodic force at the boundary with the frequency larger than the plasma frquency of the junction. It is shown that due to excitation of a standing linear wave by the driving force, the fluxon motion is strongly influenced by a periodic (averaged) potential similar to the Peierls-Nabarro potential in a discrete chain. This effective potential decreases in the direction of the boundary where the external rf drive is applied, so that the fluxon always moves to the active boundary. We calculate the fluxon parameters and confirm our analytical predictions by direct numerical simulations.