How do the United States and China perceive each other's role in the South China Sea disputes? In this paper, we trace how interactions between the US and China in the South China Sea have hardened perceptions of each other's broader strategic intentions. Based on our examination of US and Chinese views, we argue that the South China Sea disputes have evolved from a contest over sovereign rights among the claimants into a contest between the US and China over the regional order, including the balance of power and international norms and rules. On the one hand, China views US involvement in the South China Sea disputes as a threat not just to sovereignty claims but to its rise more generally. On the other hand, the United States views China's efforts to strengthen its claims and influence in the South China Sea as a threat to the regional order and US leadership in in the region. Our findings have two important implications. First, as the US and China use interactions in the South China Sea as an indicator of the other's broader strategic intentions, hardened perceptions of each other are likely to fuel adversarial perceptions in other issues. Second, unresolved territorial and sovereignty disputes may heighten the peril associated with transitions, increasing the risk that the US and China will become entangled in an escalatory spiral.