The spectacular astrophysical discoveries made by the present generation of ground-based gamma-ray observatories have opened a new era in the exploration of the highest energy Universe and have conclusively established the field of VHE astronomy. The detection of nearly one hundred galactic and extragalactic sources has generated considerable interest in the astronomy, astrophysics, and particle physics communities and has stimulated ambitious ideas and plans for future gamma-ray observatories. AGIS is a concept for a next generation VHE instrument being developed by a group of scientists from thirteen universities in US and Canada and two US National Laboratories. The efforts of the AGIS collaboration are directed towards the development of the design of a future international observatory with a collecting area on the scale of a square kilometer, significantly improved angular and energy resolution, increased field of view, and an order of magnitude increase in sensitivity over existing space or ground-based instruments in the energy range 40GeV to 100TeV. The scientific motivations, simulations, and R&D roadmap for AGIS will be discussed.