Iran will inform the U.N. nuclear watchdog in Vienna on Tuesday over its start of a process to increase the country's uranium enrichment capacity, Iran's Atomic Energy Organisation spokesman Behrouz Kamalvandi told ISNA news agency.
"In a letter that will be handed over to the International Atomic Energy Agency (IAEA) ... Iran will announce that the process of increasing the capacity to produce ... UF6 (uranium hexafluoride) ... will start on Tuesday," Kamalvandi said.
He said Iran had the capacity to accelerate production of centrifuges, which are used to enrich uranium. The UF6 is a feedstock for centrifuges.
Iran's ultimate authority Supreme Leader Ayatollah Ali Khamenei said on Monday he had ordered preparations to increase uranium enrichment capacity if a 2015 nuclear deal with world powers falls apart after the U.S. withdrawal from it last month.