A reactor configuration is proposed for selectively converting gaseous, liquid or solid fuels to a syngas specification which is flexible in terms of H2/CO ratio. This reactor and system configuration can be used with a specific oxygen carrier to hydro-carbon fuel molar ratio, a specific range of operating temperatures and pressures, and a co-current downward moving bed system. The concept of a CO2 stream injected in-conjunction with the specified operating parameters for a moving bed reducer is claimed, wherein the injection location in the reactor system is flexible for both steam and CO2 such that, carbon efficiency of the system is maximized.