A method of resource sharing between a plurality of communication networks each having a nominal resource allocation of a shared air interface resource and a resource exchange allowance is provided. A temporary resource allocation of a first air interface resource from a nominal resource allocation of a first network is initiated. Subsequently, a plurality of offer rounds are executed with each offer round comprising determining offer values for the first air interface resource. A second network is then selected in response to the determined offer values and subsequently a resource allocation message is transmitted to the second network. The resource allocation message indicates a temporary allocation of at least part of the first air interface resource from the first network to the second network. Consequently, the resource exchange allowance of the second network is reduced accordingly. Each offer round comprises receiving new offer values from the first plurality of networks.