As Web services are becoming omnipresent on the Web, quality of Web services (QoWS) support and management is becoming a hot research topic. Several frameworks for Web service selection have been proposed to support clients in selecting suitable Web services. They are very often based on a middle-tier component to make the selection decision. These solutions suffer very often from scalability problems. To deal with this issue, we propose in this paper a new architecture for Web service selection based on a federation of cooperative brokers. Each broker of the federation manages the Web services within its domain and cooperates with its peers by exchanging information about Web services, such as reputation and QoS, to better serve client requests. We have developed a prototype of the architecture and we have conducted experiments using three broker selection policies mainly "random", "round-robin", and "cooperative brokers" to evaluate the degree of fulfillment of clients' requests. Preliminary results show that the best results are obtained by using the cooperative brokers' policy.