Iran has converted most of a nuclear stockpile, which it could have turned quickly into weapons-grade uranium, into less volatile forms as part of a deal with six world powers, the UN atomic agency has reported.

The monthly update by the International Atomic Energy Agency (IAEA), announced on Thursday, showed that Iran had, as stipulated by the November 24 agreement last year with the United States, France, Germany, Britain, China and Russia, diluted half of its higher-grade enriched uranium reserve to a fissile content less prone to bomb proliferation.

The development leaves Iran with substantially less of the 20 percent enriched uranium that it would need for a nuclear warhead, the Associated Press news agency reported.

The IAEA, which has a pivotal role in verifying that Iran is living up to its part of the accord, made clear that Iran so far is undertaking the agreed steps to curb its nuclear programme.

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

The IAEA report also pointed to a new delay in Iran's construction of a plant designed to turn low-enriched uranium gas (LEU) into an oxide powder that is not suitable for further processing into highly-enriched bomb-grade uranium.

Tehran told the IAEA last month that the site would be commissioned on April 9. But Thursday's update by the UN nuclear watchdog said the commissioning had been put off, without giving any reason.

However, "Iran has indicated to the agency that this will not have an adverse impact on the implementation of (its) undertaking" to convert the uranium gas, the agency said.

Israeli vow

The delay means that Iran's LEU stockpile - which it agreed to limit - is almost certainly continuing to increase for the time being, simply because its production of the material has not stopped, unlike that of the 20 percent uranium gas.

Uranium at 20 percent is only a technical step away from weapons-grade material. By the time the agreement was reached late last year, Iran had amassed nearly 200 kilograms, Reuters news agency reported.

With further enrichment, that would have yielded almost enough weapons-grade uranium for one atomic bomb, a threshold that Israel had vowed it would prevent by any means possible.

Under the deal, Iran agreed to stop enriching to grades beyond five percent, the level most commonly used to power reactors. It also committed to neutralising all its 20 percent stockpile, half by diluting to a grade that is less proliferation-prone and the rest by conversion to oxide used for reactor fuel.

Source: Agencies