VIENNA (AP) — The U.N. nuclear agency says Iran has neutralized half of its stockpile of higher-enriched uranium that could be turned quickly into the core of a nuclear weapon.

The development leaves Tehran with substantially less of the 20-percent enriched uranium that it would need to for such a purpose. Uranium at that level is only a technical step away from weapons-grade material.

The U.N's International Atomic Energy Agency reported the development Thursday in a confidential report obtained by The Associated Press.

Iran denies any interest in atomic arms. But it has agreed to some nuclear concessions in exchange for a partial lifting of sanctions crippling its economy under a deal in effect since January.

Diluting half of its 20-percent enriched stockpile were among the Iranian commitments under the agreement.