The United Nations nuclear agency says Iran has adhered to the nuclear deal it agreed with six world powers last year limiting its stockpiles of nuclear-related substances.
But the report by the International Atomic Energy Agency released on September 8 also said Iran had begun manufacturing rotor tubes for centrifuges, machines used to enrich uranium.
Iran is allowed to make such parts but there are limitations. The report said "related technical discussions" were continuing on the question of the rotor tubes.
Earlier this month, a U.S. think tank said Iran had been secretly allowed to overstep certain thresholds in order to get the deal through on time.
But the White House has denied there were any secret deals and says the landmark agreement, negotiated by Russia, China, Britain, France, and Germany, ensures Iran cannot develop nuclear weapons.
In exchange, punishing international sanctions on Iran were lifted.
Under last year's deal, Iran is allowed to conduct certain research and development activities beyond uranium enrichment with its older-generation centrifuges.