Atomic watchdog IAEA says Tehran has installed no new major parts in its heavy water reactor in three months

Iran's new government has significantly slowed down expansion of its nuclear programme in an apparent attempt to give more time for negotiations.

A report by the International Atomic Energy Agency says over the past three months Iran has installed no new major parts in its heavy water reactor in Arak, whose construction is one of the major remaining sticking points in multilateral talks which adjourned in Geneva early on Sunday.

The Iranian stockpile of medium-enriched uranium crept up by about 10kg to 196kg. The stockpile, enriched to 20% purity, is an another leading proliferation concern, but it remains well below the estimated 250kg that would be required, with further enrichment, to make a nuclear weapon.

Just as significantly, Iran has virtually stopped the growth of its enrichment capacity. It installed no new-model centrifuges at its enrichment plant in Natanz over the past quarter, which is important as the new centrifuges, the IR-2M, can enrich uranium up to five times faster than the old model, the IR-1

Only four more IR-1 centrifuges have been added bringing the total to 15,240. None of the IR-2M are being fed with uranium hexafluoride gas to enrich, and overall the number of centrifuges being used for enrichment has stayed roughly the same since the beginning of the last year.

The slowdown in the growth of the Iranian programme comes amid the most intensive diplomacy over Iran's nuclear programme for a decade. Foreign ministers from Iran and six major powers – the US, UK, France, Germany, Russia and China – came close last week to a stopgap deal that would have rolled back elements of the programme and lifted some sanctions.

The talks stalled because of insistence, led by France, that any deal should not grant Iran the long-term right to enrich uranium and should halt work on the Arak reactor. The IAEA inspectors found that although the reactor vessel had been connected up to piping, "no other major components, such as the control room equipment, the refuelling machine and reactor cooling pumps, had been installed."

Most experts think the reactor is very unlikely to be completed on schedule by early next year.

The talks are due to resume next week in Geneva.

The Israeli prime minister, Binyamin Netanyahu, who has lobbied hard against an interim deal with Iran, said last night he was not impressed by the slowdown in the Iranian programme.