Empty streets are a rare sight in Tehran, a sprawling and congested metropolis that is home to over 15M people—except for during Nowruz, the Iranian New Year. But despite the empty streets amid the two-week annual holiday, key government buildings in Tehran are packed with their regular occupants, who have on senior levels been discussing the few remaining options to avoid a breakdown of the talks with the P4+1 (Britain, France, China, Russia and Germany) and the US to revive the 2015 Iran nuclear deal.

After a year of indirect negotiations between Iran and the Joe Biden administration, which has asserted that it seeks to reverse former president Donald Trump’s 2018 decision to...