We view a group problem as a resource allocation problem among involved parties, and negotiation as the members' act to protect, or better yet, to gain additional resources for themselves. Group members gather together to achieve a common goal. Yet, they are also stakeholders seeking to defend their own interest as well. As such, negotiation can be seen as an effort of all parties seeking to exchange viewpoints, proposing offers and counter-offers with arguments, until a solution is found or a deadlock is considered unsolvable. This paper proposes an action resource model to represent negotiation problems, and an argumentation language to support negotiation processes. The proposed action resource argumentation language is illustrated by an actual negotiation-the softwood lumber negotiation between Canada and the United States.