The possibility to generate a nondiffracting Bessel beam by means of a fast backward spatial harmonic supported by an annular metal-strip grating placed on a grounded dielectric slab is demonstrated. The focusing capabilities of the relevant leaky-wave aperture field are investigated in conjunction with the dispersive analysis of the considered structure. Full-wave simulations of a prototype are developed using a commercial code. The proposed design represents an attractive simple and low-cost solution potentially able to generate an arbitrary-order nondiffracting beam.