VIENNA (AP) — Diplomats say that a U.N. nuclear agency will confirm that Iran has met a key condition of a preliminary nuclear agreement, changing a substantial amount of enriched uranium into a form that is difficult to use for nuclear arms.

Enriched uranium can be used to generate energy or as the fissile core of a nuclear weapon, depending on its enrichment level. Under the preliminary deal reached in November 2013, Iran agreed to convert thousands of kilograms of the material into oxide form, which experts say cannot be used to build a bomb.

The diplomats said Tuesday that a report to be issued Wednesday by the U.N.'s International Atomic Energy Agency will show that Iran has complied with the obligation to render harmless the uranium it has enriched since November 2013.