Resonant excitation of an upper hybrid wave by the mixing of two coaxial Gaussian em beams in a collisionless hot magnetoplasma has been investigated; the electric vectors of beams are polarized along a uniform static magnetic field and the beams propagate perpendicular to the magnetic field. The resonant excitation of the upper hybrid wave occurs when the difference frequency of the two em waves and difference of their propagation vectors satisfy the dispersion relation corresponding to the upper hybrid wave. Furthermore, because of the Gaussian intensity distribution of the two beams the electrons are redistributed by the ponderomotive force, cross focusing of the two em beams occurs, and the power of the excited upper hybrid beam (which depends on the background electron concentration, the intensities of the two em beams, and the magnetic field) are correspondingly modified. The present analysis is also applicable to an inhomogeneous magnetoplasma in the WKB approximation.