An occlusion catheter system for full or partial occlusion of a vessel includes an occlusion balloon. The balloon is positioned in a folded, uninflated configuration around a central shaft, a proximal shaft, and a distal shaft of the occlusion catheter system, having an outer diameter less than seven French. The balloon is constructed of a semi-compliant or non-compliant material and is sized to have a blown diameter between approximately ten percent to sixty percent greater than the inner diameter of the vessel, whereby an outer surface of the balloon comes into full diametric contact with an inner surface of the vessel upon partial inflation of the balloon and folds are formed in the outer surface of the balloon. The folds define flow channels with inner surfaces of the vessel or with portions of the outer surface of the balloon that allow partial blood flow past the balloon.