For the intensive offline computation and storage needs of LHC, the Grid has become a necessary tool. The grid software is called middleware, and comes in different flavors. The ALICE experiment has developed AliEn, while ARC has been developed in the Nordic countries. The Nordic community has pledged to LHC a large amount of resources distributed over four countries, where the job management should be done in a unified way using ARC. We have developed an interoperation module in AliEn to this purpose, so that an group of sites can look like a single site to AliEn. A prototype has been completed and tested out of production. This talk will present implementation details of the system and its performance in tests.