Many nations agreed to a global system consisting of the international conventions for oil spill liability and compensation. On the other hand, a concern about the adequacy of the international regime induced the U.S. to take a unilateral approach instead of joining the international regime. With significant differences in detail, both regime share a structure based on the same basic principles. Both regimes have a two tier structure that is composed of a liability scheme and a fund scheme. Each regime imposes liability on the shipping sector based on the principle that the polluter pays. In addition, each regime establishes a fund financed by levies imposed on shipped oil to supplement the primary liability scheme. The disparities between the international and U.S. regimes in the function of funds will be reviewed as a premise for discussion of feasibility of a unified international regime. The peculiarities recealed in the process of nationalization of the international regime can be interpreted as a limitation of harmonizing the regimes. On the other hand, they can make it easier to formulate a unified international regime by differentiating national regimes. The review of advantages and disadvantages in each regime implies what a new unified international regime should be.