We explore negotiation as the basis for cooperation between competing entities, for the specific case of routing between two neighboring ISPs. Interdomain routing is often driven by self-interest and based on a limited view of the internetwork, which hurts the stability and efficiency of routing. We present a negotiation framework in which adjacent ISPs share information using coarse preferences and jointly decide the paths for the traffic flows they exchange. Our framework enables pairs of ISPs to agree on routing paths based on their specific relationship, even if they have different optimization criteria. We use simulation with over sixty measured ISP topologies to evaluate our framework. We find that the quality of negotiated routing is close to that of globally optimal routing that uses complete, detailed information about both ISPs. We also find that ISPs have incentive to negotiate because both of them benefit compared to routing independently based on local information.