The present invention is directed to a one-component polyurethane or polyurea composition which is based ona) a liquid blocked polyisocyanate wherein the isocyanate groups have been blocked with a phenolic blocking agent andb) a solid polyamine which is insoluble in and dispersed throughout the liquid blocked polyisocyanate,wherein the composition may be cured at elevated temperature and also at ambient temperature if the solid polyamine contains nonaromatically bound amino groups.The present invention is also directed to a process for the preparation of a high molecular weight polymer by heating the one-component composition at elevated temperature or by adding a polar solvent to the coating composition and allowing the composition to cure at ambient temperatures, provided that the solid polyamine contains nonaromatically bound amino groups.