VIENNA (Reuters) -Iran is almost ready to start enriching uranium to 60% purity at an above-ground plant at Natanz and plans to add 1,024 first-generation IR-1 centrifuges to an underground plant Tehran says was hit by sabotage, the U.N. atomic watchdog said on Wednesday. Iran has said it will enrich uranium to 60% - a big step closer to the 90% that is weapons-grade from the 20% maximum it has reached so far - in response to what it says was an act of sabotage by Israel against the underground plant. “The Agency today verified that Iran had almost completed preparations to start producing UF6 enriched up to 60% U-235 at the Natanz Pilot Fuel Enrichment Plant (PFEP),” the International Atomic Energy Agency said in a statement, referring to uranium hexafluoride, the form in which uranium is fed into centrifuges for enrichment. Iran’s nuclear deal with major powers only lets Tehran enrich uranium to up to 3.67% purity, one of many limits that it breached more than a year ago in response to Washington’s withdrawal from the deal under President Donald Trump and the reimposition of U.S. sanctions against Tehran. The deal also says Iran can only produce enriched uranium with up to 5,060 IR-1 centrifuges at its underground Fuel Enrichment Plant (FEP) at Natanz. While it has broken that rule by adding more advanced centrifuges to the FEP, until now it has stuck to the limit on the number of IR-1 machines there. “In a report issued to Member States today ... Director General Rafael Mariano Grossi said Iran had informed the Agency ... that the country intends to install six additional cascades of IR-1 centrifuges at the Natanz Fuel Enrichment Plant (FEP) comprising a total of 1,024 centrifuges,” the IAEA said. That report, one of two issued on Wednesday evening and obtained by Reuters, added: “Iran intends to use 6,084 IR-1 centrifuges installed in 36 cascades (in total at the FEP).” The United States and Iran will reconvene indirect talks aimed at reviving the 2015 Iranian nuclear deal on Thursday in Vienna, White House press secretary Jen Psaki said.