Tehran has \"no reason\" to suspend its enrichment of uranium to 20 percent -- one of the key demands of world powers engaging Iran in talks -- the head of its Atomic Energy Organisation said. \"We have no reason to cede on 20 percent, because we produce only as much of the 20 percent fuel as we need. No more, no less,\" Fereydoon Abbasi Davani was quoted as saying late Saturday by the ISNA and Mehr news agencies.