UN atomic watchdog head says additional understandings must lay out how Iran's violations of multilateral accord can be reversed, as parties are no longer at 'square one'

Joint commission representing China, France, Russia, Germany, Britain and Iran meets in effort to prevent total breakdown of 2015 agreement before Biden enters office

Meeting of remaining signatories to 2015 nuclear deal in Vienna look to keep accord alive, despite US withdrawal, sanctions and Iranian violations

As Tehran resumes nuclear development, nations have threatened to bring case before UN Security Council and potentially initiate 'snapback' of sanctions