The Biden administration negotiated to get back into the Iran nuclear deal but could not, partly because Iranians questioned the reliability of a new U.S. commitment after Trump pulled out.

“The Biden administration began negotiations in Vienna in April 2021 to restore the 2015 nuclear deal (JCPOA). However, the talks stalled and ultimately failed. A key sticking point was Iran's demand for guarantees that a future U.S. administration would not unilaterally withdraw from the agreement again, as the Trump administration did in 2018. Iranian officials repeatedly stated the need for "confidence-building guarantees" to ensure they would receive the promised economic benefits, a demand the U.S. could not legally provide for future administrations. Context: The negotiations were indirect, with European diplomats shuttling between U.S. and Iranian officials. Other points of contention included the scope of sanctions relief and Iran's demands that the U.S. lift the Foreign Terrorist Organization (FTO) designation on the Islamic Revolutionary Guard Corps (IRGC).”