Iran's output of enriched uranium is stagnating even as its production capacity increases, a sign that Tehran may be running out of the ore needed to make nuclear fuel, diplomats said. If so, it could mean that international sanctions to slow if not stop Iran's nuclear program are taking hold.

The diplomats - who demanded anonymity because their information was confidential - emphasized the possibility that Iran was running short of uranium oxide was only one of several possible explanations for why it had not substantially upped its production of enriched uranium since May.

But they said Tuesday it seemed unlikely the Islamic Republic had deliberately decided to curb production. They noted that over the past three months the country has expanded its processing capabilities by installing and running hundreds more of the centrifuges used to enrich uranium.

The U.N. Security Council has imposed sanctions against Iran three times since 2006 for its refusal to freeze uranium enrichment. The sanctions grew from fears that Iran is using the pretext of building a peaceful nuclear energy program as a guise to eventually make weapons-grade enriched uranium.

The country has also been placed on an international watch list to help limit the importation of nuclear materials, which could make it difficult to procure enough uranium oxide to feed its enrichment program.

The International Atomic Energy Agency and independent experts believe that Iran's rapidly expanding uranium enrichment program has been built on 600 tons of so-called "yellowcake" or uranium oxide imported from South Africa during the 1970s. The material was procured as part of ambitious plans by the former regime of Shah Mohammad Reza Pahlavi to build a network of nuclear reactors to generate power.
Iran denied it was running out of yellowcake. "It is not true," said Ali Asghar Soltanieh, Tehran's chief delegate to the IAEA, while adding that he could not make a substantial comment before the agency publishes its next report on his country's nuclear program sometime this week.

"This is a technical project with its ups and downs," he told the AP, when asked whether output was stagnating. "But everything is going according to plan." At the State Department, spokesman Ian C. Kelly declined to comment, except to say that the U.S. remains intent on stopping Iran from getting a nuclear weapon.

Diplomats: Iran's enrichment program stagnates - Hürriyet Daily News and Economic Review