Dynamics, the spectral and eigenstate properties of two particles with short range repulsive or attractive interaction was studied in the Harper model with incommensurate potential [84,85,87]. It is shown that interaction leads to appearance of localized states and pure-point spectrum component in the case when noninteractive system is quasi-diffusive or ballistic. In the localized phase interaction gives only stronger localization contrary to the case of two interacting particles in a random potential. These results were qualitatively understood on the basis of Aubry duality breaking.