The UN nuclear watchdog was expected to issue a monthly update later on Wednesday showing Iran is complying with the terms of last year's interim deal with six world powers to curb some of its atomic activities, diplomats said.
The UN International Atomic Energy Agency (IAEA) is tasked with checking that Iran is living up to its part of the agreement that took effect in January and was last month extended by four months until late November.
Under the accord that was reached in late 2013 - meant to buy time for negotiations on a permanent settlement of the decade-old dispute - Iran halted its most sensitive nuclear work in exchange for some easing of sanctions.
The initial aim was for Iran and the six powers - the United States, France, Russia, China, Britain and Germany - to reach a comprehensive agreement by a self-imposed July 20 deadline.
But the talks and the preliminary deal were extended in view of still wide differences over the permissible future scope of Iran's uranium enrichment program, activity which can have both civilian and military purposes.
Iran denies Western allegations that it has been working to develop a capability to make atomic bombs, saying it is only refining uranium to fuel a planned network of nuclear power plants.
After years of escalating tension between Iran and the West, the election in mid-2013 of Hassan Rouhani, a pragmatist, as new Iranian president on a platform of ending Tehran's international isolation created new room for diplomacy that ultimately led to last year's breakthrough nuclear accord.
The Vienna-based IAEA has inspectors on the ground in Iran who are monitoring its nuclear sites. Its monthly reports on the implementation of the nuclear agreement are issued to its member states and not made public.