Iranian President Hassan Rouhani (second right) listens to head of the Atomic Energy Organization of Iran Ali Akbar Salehi while visiting an exhibition of Iran’s new nuclear achievements in Tehran on Saturday.

In this photo released by the official website of the office of the Iranian Presidency, President Hassan Rouhani, second right, listens to head of the Atomic Energy Organization of Iran Ali Akbar Salehi while visiting an exhibition of Iran’s new nuclear achievements in Tehran, Iran, Saturday, April 10, 2021. Iran said Saturday it has begun mechanical tests on its newest advanced nuclear centrifuge, even as the five world powers that remain in a foundering 2015 nuclear deal with Iran attempt to bring the U.S. back into the agreement. (Iranian Presidency Office via AP)