Iran's nuclear chief reportedly said Sunday that Tehran has launched “preliminary activities for designing” uranium fuel with a purity of 20 percent, a move that would be at odds with the 2015 nuclear deal.

“Preliminary activities for designing modern 20 percent [enriched uranium] fuel have begun,” Ali Akbar Salehi said in remarks covered by state television, according to multiple reports.

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The nuclear deal that Iran reached in 2015 with world powers prevented Tehran from enriching uranium above 3.67 percent. Iran was reaching 20 percent before the deal.

President Trump Donald John TrumpHR McMaster says president's policy to withdraw troops from Afghanistan is 'unwise' Cast of 'Parks and Rec' reunite for virtual town hall to address Wisconsin voters Biden says Trump should step down over coronavirus response MORE has already pulled the U.S. out of the deal, which lifted sanctions on Iran in exchange for limits on its nuclear program.

Reuters reported that Iran is permitted to produce nuclear fuel under certain conditions that must be approved by a working group convened by signatories of the deal, also known as the Joint Comprehensive Plan of Action.

“We have made such progress in nuclear science and industry that, instead of reverse-engineering and the use of designs by others, we can design new fuel ourselves,” Salehi was quoted telling state television, according to the news service.

Salehi also said that the product Iran is beginning to develop "is different from the previous 20 percent fuel."