A new microscopic kinetic model of coupled nonequilibrium condensation and radiative excitation of water molecules effusing from a surface of a cometary nucleus is developed. The method is greatly based on the microscopic theory of nonequilibrium condensation (MTC) developed earlier by the author. To analyze vibrational and rotational excitation of the H2O molecule a kinetic model has been used which includes infrared rovibrational pumping by the solar radiation flux, thermal excitation by collisions, and radiation trapping in the rotational and rovibrational lines. Appropriate kinetic equations for cluster concentrations and populations of their energetic levels have been solved analytically. This permits one to reduce the coupled equations of the condensation and radiative balance to a closed system of differential equations involving the rotational populations of the water molecule. Prospects of the use of this model when studying an influence of the indicated processes on the structure of an inner coma are discussed.