Iran is sticking to a six-month nuclear freeze agreed to under a November interim deal with world powers, the UN atomic agency said in a new report on Thursday, a month after the agreement came into force.

The International Atomic Energy Agency update said that uranium enrichment to medium levels - the main concern of the international community - "is no longer taking place", as stipulated in the deal.

The IAEA also said a proportion of Iran's medium-enriched uranium stockpile, as set out in the November deal, which took effect on Jan 20, "is being downblended and the remainder is being converted to uranium oxide".

Enrichment to low purities, however, "continues at a rate of production similar to that indicated" in the last report from November, meaning that its stockpile that material grew in the last three months.

This is consistent with the agreement with world powers, as long as by the end of the six-month period on July 20 the stockpile is not larger than at the start.

Iran is currently building a facility to convert this type of material to oxide form, the IAEA report said, from which it would be more difficult to enrich to weapons-grade.

In addition, Iran has not installed any additional uranium- enrichment centrifuges at either of its facilities, Natanz and Fordo, according to the IAEA.

Regarding a reactor being constructed at Arak, the IAEA said: "No additional major components have been installed at this reactor and there has been no manufacture and testing of fuel for the reactor."

The agency also said Iran has provided it with a so-called design information questionnaire for Arak, and that access was granted to centrifuge assembly workshops, centrifuge rotor production workshops and storage facilities.

But Israel, which alongside Western nations suspects Iran of seeking nuclear weapons capability, insisted that the report proved once again that the interim agreement "did not address the military component of Iran's nuclear program".

"The report reiterates that the (IAEA) cannot confirm Iran's nuclear program is solely for peaceful purposes," an Israeli government official said in a statement.

And while sanctions have been significantly eased, "Iran has made no real concessions in its nuclear program," the official said.

Chief US negotiator Wendy Sherman will head from Vienna to Israel to brief the government of Prime Minister Benjamin Netanyahu on the talks.

Earlier on Thursday, Iran and the six powers - the United States, China, Russia, Britain, France and Germany - agreed on a timetable and a framework for negotiating a lasting nuclear accord, which could resolve the decade-old standoff over Iran's nuclear drive.

The IAEA report also revealed for the first time that under previous president Mahmoud Ahmadinejad, Iran had started but not finalized "preliminary site selection" for five new uranium enrichment facilities.

"This was something that happened under the previous president," a senior diplomat familiar with the agency's work said, describing it as a "very preliminary process".