A liquid composition for glass fiber impregnation, characterized in that (A) it comprises (1) a resorcinol-formaldehyde resin, (2) a butadiene/styrene/vinylpyridine terpolymer, and (3) chlorosulfonated polyethylene, and (B) based on the total solids of the components (1), (2) and (3), the proportion of component (1) is 2 to 15% by weight, the proportion of component (2) is 15 to 80% by weight, and the proportion of component (3) is 15 to 70% by weight; and a glass fiber cord having a solid coating derived from the liquid composition. The glass fiber cord is useful as a reinforcing material in products, such as timing belts, which undergo both heat and an external force during travelling.