Talks between six world powers and Iran aimed at defusing the Iranian nuclear threat have failed to bring about a breakthrough. After two days of meetings in Moscow which ended without progress, Iran's senior nuclear negotiator Saeed Jalili said: "We emphasized that uranium enrichment is the inalienable right of the Iranian nation.” He added that Iran's leadership had issued a fatwa that prevented the production and use of weapons of mass destruction.

European Union foreign policy chief Catherine Ashton described the talks as "detailed, tough and frank exchanges." The Iranians "did begin to address the substance for the first time, but there's a very, very long way to go, and I'm sure that Dr. Jalili would say that, too," Ashton told reporters.

The parties have agreed to hold a technical-level meeting in Istanbul on 3 July, where experts in nuclear technology would work out details, she said. "The choice is Iran's," Ashton said. "We expect Iran to decide whether it is willing to make diplomacy work, to focus on reaching agreement on concrete, confidence-building steps and to address the concerns of the international community."

The six world powers are demanding that Iran suspend enrichment of uranium to 20 percent, close down an underground enrichment facility near the city of Qom and export its stockpile of 20 percent-enriched uranium - measures described by one Western diplomat as "stop, shut and ship". In return, the world powers say they are prepared to start by offering help with nuclear safety measures. However, Iran wants the West to lift the sanctions currently in place, including an EU oil embargo and US measures against Iran's central bank.

Meanwhile, French Foreign Minister Laurent Fabius said it would continue to strengthen sanctions against Tehran. “We regret that Iran has still not made the concrete gestures that we were waiting for and that could constitute a first step towards respecting UN Security Council and IAEA resolutions," Fabius was quoted by the ‘Reuters’ news agency as saying. He added that pressure on Iran would be increased with the full implementation of a European Union oil embargo beginning on 1 July.

Fabius said that sanctions would continue “as long as Iran refuses serious negotiations." The six world powers negotiating with Tehran – Britain, China, France, Germany, Russia and the United States – would evaluate what steps to take next after the technical meetings in Istanbul.