In a further move away from the 2015 nuclear deal with world powers, Iran has started enriching uranium with a third cascade, or cluster, of advanced IR-2m centrifuges at its underground plant at Natanz, Reuters reported on March 8, citing a report by the UN nuclear watchdog.

Monitors of the International Atomic Energy Agency (IAEA) on March 7 verified that Iran began feeding uranium hexafluoride, the feedstock for centrifuges, into the third cascade, the Vienna-based agency said in the report to its member states that was obtained by Reuters.

The report said a fourth cascade of 174 IR-2m centrifuges had been “installed but had yet to be fed with natural UF6,” adding that a fifth cascade of IR-2m centrifuges “was ongoing.”

Under the 2015 nuclear agreement, which aimed to restrict Iran’s nuclear program in exchange for relief from sanctions, Tehran can only use first-generation IR-1 centrifuges, which refine uranium much more slowly, at Natanz.

Tehran has gradually rolled back its commitment under the accord in response to a 2018 decision by former U.S. President Donald Trump to withdraw the United States from the pact and reimpose sanctions that have crippled Iran’s economy.

Iran has in past weeks accelerated its nuclear activities in what could be an attempt to pressure the new administration of U.S. President Joe Biden, which has signaled its readiness to revive the deal but insists Iran first return to all its nuclear commitments.

Meanwhile, Tehran says it first wants sanctions to be lifted.

Based on reporting by Reuters