In this talk, we will analyze the impasse, caused by polarizing positions of the United States and China–in international negotiations on carbon mitigation. By incorporating the Bern carbon cycle module into the RICE model developed by Nordhaus and Yang (1996), we set up a framework for tracking regional contributions to carbon concentration and to global climate change. Our proposal, labeled the “color preservation” principle, uses regional contribution share to global carbon concentration as the criterion for international cooperation. Through simulations in RICE model with Bern module (RICE-B), we examine the rationales of the arguments made by the United States and China. We conclude that both countries' standpoints are severely flawed. To facilitate the global cooperation on carbon mitigations, major concessions are needed from the two top carbon emitters.