In this paper a system for goal directed integration of web services based on automated planning is presented. The increasing number of web services available on the net poses the problem of having efficient tools in order to integrate existing services for obtaining complex services which reflect user goals and needs. In this scenario, automated planning techniques represent promising components of such dynamical and evolutionary systems. In the proposed architectural model, web services and user goals are modeled as planning operators and goals, while the generated solution plans are used for directly generating web service scripts. An extended planning model based on the notion of output variable has been introduced in order to take into account of results produced by services invocations. A technique called semantic wrapper has been developed for modeling services as operators. In addition to a simple automation tasks, web services plans also optimise's the use of resources, and they provides useful information on variables bindings and the parallel structure of web services calls. The implementation of P4WS, a planner with output variables which demonstrated the model is described and experimental results are presented.