NUCLEAR INSPECTORS

The Geneva deal was designed to halt Iran's nuclear advances for six months to buy time for negotiations on a final settlement. Scope for diplomacy widened after Iran elected the pragmatic Hassan Rouhani as president in June. He had promised to reduce Tehran's isolation and win sanctions easing.

Separately, diplomats in Vienna said the UN nuclear agency could face costs of roughly 5 million euros ($6.9 million) to verify that Iran lives up to the deal.

The 35-nation governing board of the UN International Atomic Energy Agency is expected to hold an extraordinary meeting next month to discuss the IAEA's expanded role.

The extra cost is unlikely to create any major difficulty in view of the political importance of resolving the dispute.

However, diplomats accredited to the UN agency said it could be sensitive as IAEA Director General Yukiya Amano likely needs both to seek member state help to pay for more inspections in Iran and find some of the money internally.

The IAEA's budget for 2014 is around 344 million euros.

The IAEA - tasked with preventing the spread of nuclear weapons - regularly inspects Iranian nuclear sites to make sure there is no diversion of atomic material for military purposes.

But it will step up the frequency of its visits to the uranium enrichment sites of Natanz and Fordow under the Geneva agreement and also carry out other additional tasks in inspecting nuclear-linked facilities.

The agency has two to four staff in Iran virtually every day of the year, with some 20 dedicated to inspector activity there, but that number is now likely to rise.