Iran has informed the United Nations nuclear watchdog of "tentative" plans to produce the feedstock for centrifuges, the machines that enrich uranium, the agency has said.
It comes after Iran said it was preparing to increase its enrichment capacity.
The country's Supreme Leader Ayatollah Ali Khamenei said yesterday that he had ordered preparations to increase uranium enrichment capacity if its nuclear deal fell apart after US President Donald Trump announced his country's withdrawal last month.
European powers are scrambling to salvage the deal, which imposes restrictions on Iran's nuclear activities in exchange for lifting sanctions.
"The Agency received a letter from Iran on 4 June informing the Agency that there is a tentative schedule to start production of UF6," a spokesman for the International Atomic Energy Agency (IAEA) said, referring to uranium hexafluoride, the feedstock for centrifuges.
The deal allows Iran to enrich uranium to 3.67% - far below the 90% of weapons grade - and caps its stock of enriched uranium hexafluoride at 300kg.
Israeli Prime Minister Benjamin Netanyahu has said the Iranian plan is aimed at producing nuclear weapons to be used against Israel.
"Two days ago, Ayatollah Khamenei, Iran's supreme leader, stated his intention to destroy the State of Israel," Mr Netanyahu said in a video posted on social media.
"Yesterday he explained how he would do it - by unlimited enrichment of uranium to create an arsenal of nuclear bombs."
"We're not surprised," Mr Netanyahu added in the video from Paris, where he met French President Emmanuel Macron. "We won't let Iran obtain nuclear weapons."
Speaking after the meeting, Mr Netanyahu said he had not asked France to leave the nuclear agreement because he believed it would not survive after the United States pulled out of the accord and reimposed sanctions on Tehran.
"I didn't ask France to withdraw from the JCPOA (Iran deal) because I think it is basically going to be dissolved by the weight of economic forces," Mr Netanyahu told a joint news conference with President Macron.
