On 21 October, Iranian Supreme Leader Ayatollah Ali Khamenei finally endorsed Iran’s nuclear accord with world powers in a letter to President Hassan Rouhani. Khamenei said he appreciated the work of Iran’s diplomats in reaching the 14 July Joint Comprehensive Plan of Action (JCPOA), the international agreement limiting Iran’s nuclear programme in return for the lifting of economic sanctions.

However, he warned the government to remain vigilant over any failure to deliver on commitments to remove sanctions by European nations and the US.The agreement had already been approved by the Majlis (parliament) after extensive debate, by the national security body and by the Guardian Council, which vets all policy. Khamenei’s conditional approval will boost the position of Rouhani who has faced harsh criticism from hardline conservatives.

Khamenei said modifications to the heavy-water reactor at Arak, and the transfer and elimination of Iran’s stockpiles of enriched nuclear materials will only take place after the International Atomic Energy Agency (IAEA) has finalized its assessment of potential military dimensions of Iran’s nuclear programme. IAEA inspectors have ended their 12-year investigation into Iran’s past nuclear activity and have until 15 December to draft and present a final assessment of their inquiry.

Khamenei’s letter came two days after the formal "Adoption Day" of the JCPOA, marking the start of preparations for implementation of the respective commitments of both sides.

The JCPOA was signed by Iran and the E3/EU+3 (China, France, Germany, Russia, the UK and the USA plus the European Union). For Iran, this means mothballing thousands of centrifuges, eliminating 95% of its enriched-uranium stockpile over the next 15 years and retrofitting the Arak research reactor. The US and Europe will make preparations to lift sanctions, once the Iranian measures are in place.

US president Barack Obama issued a presidential memorandum directing the heads of all relevant government departments and agencies to begin preparations to implement US commitments including relief from nuclear-related sanctions once the IAEA has verified that Iran has completed all of its nuclear steps. China, the USA and Iran also released a joint statement of intent on the future steps for modifying the Arak reactor as specified under the JCPOA. This includes the removal of its existing calandria and rendering it inoperable.

The three partners are to set up a working group for facilitating the modernization project. The countries will be represented by the China Atomic Energy Authority (CAEA); the US Department of Energy (DOE); and, the Atomic Energy Organization of Iran. The working group will meet in the coming weeks.

Sanctions should be lifted within the first quarter of 2016 provided the IAEA confirms Iran has met its commitments. Once the restrictions are removed, relief is expected to fuel economic growth by lowering barriers to Iran’s oil exports and ending the isolation of its banks. Iran has said it will offer about 50 energy projects to investors and plans to boost output by about 2m barrels a day, Bloomberg reported. Japan planned to triple its imports of Iranian crude once sanctions were lifted, the Iranian oil ministry’s Shana news agency said.

Iran has notified the IAEA that it will provisionally apply the Additional Protocol to its Safeguards Agreement, pending its ratification by parliament. This will give the IAEA greater access to Iran’s nuclear facilities and research. Iran had been a signatory to the protocol from 2003 until 2006 before pulling out of the agreement when talks with the EU broke down.

Russia expects to begin shipping enriched uranium from Iran in early 2016, Vladimir Voronkov, head of the Russian delegation at the first meeting of the JCPOA, said on 19 October. "The main documents on Fordow and uranium have been worked out [and] the implementation of these measures will begin in late January or early February next year, if there are no surprises," he said, according to Interfax.