The preparation of phenol-formaldehyde and melamine-formaldehyde resin-based binders extended with a cyclic urea-formaldehyde prepolymer and to products prepared using the binders. More particularly, the invention relates to a cyclic urea prepolymer comprising urea, formaldehyde, and ammonia or a primary amine which, when added to a phenol-formaldehyde or melamine-formaldehyde based resin, results in a useful binder for the manufacturer numerous articles.