VIENNA (AP) — The United Nations will release a report this week certifying that Iran’s ability to make a nuclear bomb has been greatly reduced because it has diluted half of its material that can be turned most quickly into weapons-grade uranium, diplomats said Tuesday.

The move is part of Iran’s commitments under a deal with six world powers in effect since January that mandates some nuclear concessions on the part of Tehran in exchange for a partial lifting of sanctions crippling its economy.