The authors propose a model for the investigation of mode conversion near two ion hybrid and cyclotron harmonic resonances in axisymmetric toroidal plasmas. The wave differential equations are derived from Maxwell-Vlasov equations using this model and the assumption of weak dispersion, and are shown to coincide with equations recently obtained in the literature for a slab model including a (B0. Del )B0 term. At the same time the limits of applicability of these equations in a Tokamak are clarified. The wave equation is solved explicitly in two cases of physical interest: near an isolated two-ion hybrid resonance, where the fast wave couples to the cold torsional Alfven wave, leading mainly to electron heating; and near the first harmonic resonance of a single species plasma, where it couples to an ion Bernstein wave. These solutions clarify some aspects of the physics of these resonances, and can be useful for applications in numerical ICR heating codes.