Iran and the UN nuclear watchdog agreed Monday on a “roadmap for cooperation” over Tehran's controversial atomic drive, as the US accused Iran of scuttling latest efforts to end the deadlock.

The announcement of the breakthrough came during a visit to Tehran by International Atomic Energy Agency (IAEA) chief Yukiya Amano. No details of the accord were immediately released.

“The joint statement that was signed today details a roadmap for cooperation that determines mutual steps to resolve remaining issues,” Iranian nuclear chief Ali Akbar Salehi said at a joint news conference with Amano, which was closed to Western media in Tehran.

Amano hailed the deal as “an important step” but added “much more must be done”, in remarks were carried by the ISNA news agency.

The IAEA chief's visit is aimed at resolving technical issues linked to the IAEA's role of monitoring Iran's nuclear activities.

Broader questions of how to ensure the Islamic republic's nuclear programme is not being used to mask a drive for atomic weapons are being discussed in rounds of negotiations between Iran and P5+1 powers -- Britain, France, the United States, Russia and China plus Germany.

In the latest talks, a marathon session in Geneva which ended inconclusively on Sunday, hopes for a deal had soared after top diplomats rushed to join the talks.

But they faded as cracks began to appear among world powers when France raised concerns over a heavy water reactor being built at Arak.

Addressing the issue Monday in Abu Dhabi, US Secretary of State John Kerry accused Iran of being responsible for the failure of the talks.

"The P5+1 was unified on Saturday when we presented our proposal to the Iranians... But Iran couldn’t take it, at that particular moment they weren’t able to accept," said Kerry, who is on a regional tour to address thorny issues such as the Middle East peace process, Iran's nuclear programme and the Syrian conflict.

In the remarks he made to reporters during a visit to the United Arab Emirates capital, Kerry reassured Israel that the deal will better protect it.

"What we are doing will protect Israel more effectively," he said, as the United States and Israel were locked in an escalating war of words over the negotiations.

The P5+1 group and Iran will reconvene again in Geneva on November 20 to try to iron out differences.

The broad outline of the agreement is said to include a freeze of part or all of Tehran's nuclear programme in return for the easing of sanctions.

Close to an agreement

France said Monday that world powers and Iran were close to an agreement despite the failure of the Geneva talks.

"We are not far from an agreement with the Iranians but we are not there yet," French Foreign Minister Laurent Fabius said on Europe 1 radio.

Responding to criticism that Paris was behind the failure in Geneva because of its reservations about parts of the deal on the table, he retorted: "France is neither isolated nor a country that follows the herd. It is independent and works for peace."

Iran's nuclear chief Salehi said on Monday that as a gesture of goodwill, IAEA inspectors would be allowed to visit the heavy water production plant in Arak as well as the Gachin uranium mine in the south.

At least a year from being completed, the Arak reactor is a major source of concern for Western powers who fear the plutonium it will produce as a by-product could provide Iran with a second route for making fissile material for an atom bomb.

Iran has long been adamant it solely wants to produce isotopes for medical and agricultural purposes at the Arak plant.

Iran denies seeking or ever having sought nuclear weapons, and says such claims are based on faulty intelligence from agencies such as the CIA and Israel's Mossad.

The IAEA in particular wants to visit the Parchin military base, southeast of Tehran, where intelligence evidence suggests Iran may have carried out weaponisation research.

Salehi and Amano did not mention Parchin as being part of the deal they struck, although details of the agreement are yet to be publicised.