Iran halted production of 20 percent enriched uranium on Monday, marking the entry into force of an landmark deal with world powers on its disputed nuclear programme.

After nearly a decade of negotiations between Western powers and Iran over its nuclear drive, which the West suspected was aimed at developing weapons despite Tehran's denials, the two sides reached the interim agreement in November.

And the powers kept to their part of the deal, with both the European Union and United States announcing they were easing crippling sanctions on Iran.

The move came as the United Nations invited Iran to a peace conference on the war in Tehran's ally Syria, despite objections from Arab and Western nations.

Implementation of the nuclear deal also started the clock on negotiating a trickier long-term accord to end the nuclear standoff and avert a possible war.

Under the deal Western powers are to loosen the sanctions in a package worth $6-7 billion, including $4.2 billion in frozen overseas foreign exchange assets, in eight instalments starting February 1.

Mohammad Amiri of Iran's Atomic Energy Organisation said Tehran had honoured its side of the deal reached with the P5+1 powers -- UN Security Council permanent members Britain, China, France, Russia and the United States plus Germany.

“In line with the implementation of the Geneva joint plan of action, Iran suspended the production of 20 per cent enriched uranium in the presence of UN nuclear watchdog inspectors at Natanz and Fordo sites,” Amiri told state media.

The International Atomic Energy Agency confirmed Iran “has ceased enriching uranium above five percent” fissile purities at the Natanz and Fordo enrichment facilities, the IAEA said in a report passed to member states and seen by AFP.

It said Iran was also converting its stockpile of medium-enriched uranium, a particular concern to the international community since it could easily be purified to weapons-grade.

The IAEA said Iran “is not conducting any further advances to its activities” at Natanz, Fordo or the heavy-water reactor under construction at Arak, which could provide weapons-grade plutonium.

“It's all fine, all their requirements have been fulfilled,” a diplomat told AFP.

British Foreign Secretary William Hague said Monday's implementation was a key milestone but stressed “it is important that other sanctions are maintained and the pressure is maintained for a comprehensive and final settlement”.

Source: AFP