This paper presents a computational approach to modelling pragmatic and semantic aspects of multi-issue bargaining dialogues. The model accounts for actions that shape negotiation structure and actions that express negotiation strategies. The model also accepts a number of negotiation moves as specifications of the semantic content of the performed task-related dialogue acts. The designed dialogue context model specifies the creation, maintenance and transfer of participants' private and shared beliefs. A negotiation agent that operates on this basis was implemented and evaluated against human performance. The approach allows efficient interpretation and generation of negotiation behaviour according to different negotiation strategies.