Many day-to-day tasks require negotiation, mostly under conditions of incomplete information. In particular, the opponent's exact tradeoff between different offers is usually unknown. We propose a model of an automated negotiation agent capable of negotiating with a bounded rational agent (and in particular, against humans) under conditions of incomplete information. Although we test our agent in one specific domain, the agent's architecture is generic; thus it can be adapted to any domain as long as the negotiators' preferences can be expressed in additive utilities. Our results indicate that the agent played significantly better, including reaching a higher proportion of agreements, than human counterparts when playing one of the sides, while when playing the other side there was no significant difference between the results of the agent and the human players.