The news comes as Iranian Foreign Minister Javad Zarif called on Cornel Feruta, acting chief of International Atomic Energy Agency and his inspectors "to observe the principles of professional work, maintain confidentiality of activities, and keep doing its duties impartially".
Iran last week announced its intention to use the centrifuges and has already surpassed the levels set by the accord on enriching uranium in an effort to get the countries still participating to help ease economic sanctions imposed by the U.S. after the United States withdrew from the deal last May.
Under the atomic accord, Iran is limited to operating 5,060 older IR-1 centrifuges.
The United States, which pulled out of the nuclear deal previous year by President Donald Trump, is trying to force Iran to negotiate a more sweeping agreement, covering Tehran's ballistic missiles and regional behaviour, than the current accord.
Iran has doubled the number of certain advanced centrifuges for enriching uranium, the International Atomic Energy Agency (IAEA) confirmed on Monday, after Tehran said it would take further steps away from its nuclear deal with major powers.
Defense Secretary Mark Esper says he's "not surprised" Iran is violating terms of 2015 nuclear agreement; Lucas Tomlinson reports from the Pentagon. It can use far fewer advanced centrifuges for research but without accumulating enriched uranium.
While uranium is one of only two materials that can be used to manufacture a nuclear warhead, one of the diplomats said that the IAEA had determined whatever material was stored there was not highly enriched, "meaning it was not purified to a level anywhere close to that needed for weapons", Reuters wrote.
Beijing blames US for Iran nuclear tensions
Its collapse started with the United States unilaterally withdrawing from the deal a year ago and imposing increased sanctions. But it did say Iran's cooperation could be better. He said the US and other IAEA member states were "eager to get a full report as soon as possible".
The IAEA head said during his meetings in Tehran he "stressed the need for Iran to respond promptly to Agency questions related to the completeness of Iran's safeguards declarations", adding, "Time is of the essence".
Speaking later on Monday to reporters in Vienna, Feruta described his exchanges with Iranian officials as "very substantial" and said he "was pleased with the tone and the input we received in those conversations".
Foreign Ministry spokeswoman Hua Chunying said Monday: "The U.S. should abandon wrong practices such as unilateral sanctions and maximum pressure on Iran".
Her comments followed Iran's announcement that it would start using advanced centrifuges that are prohibited under the agreement.
"We call on Iran to meet its commitments under the JCPOA and to return to them", Breul said.
President Trump's National Security Adviser, a long-time hawk on Iran, alluded to the revelation that uranium was found at the facility in a tweet over the weekend, saying it proved Iran "may be concealing nuclear material and/or activities".More news: Hailee Steinfeld Offered The MCU Role Of Kate Bishop In 'Hawkeye' Series
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