Iran rejected on Sunday an invitation from global powers who signed the 2015 nuclear deal to discuss the regime’s potential return to the negotiating table, a significant setback in the Biden administration’s efforts to revive the agreement. The Biden administration has previously said that it wants to revive the nuclear deal but won’t suspend sanctions until Tehran comes back into compliance. Tehran has refused to negotiate while U.S. sanctions remain in place. The 2015 Joint Comprehensive Plan of Action (JCPOA), brokered by the Obama administration, lifted sanctions on Iran that had crippled its economy and cut its oil exports roughly...