Ali Bagheri Kani arrives in Austrian capital following sudden trip back to Tehran, with EU envoy indicating new agreement awaiting Islamic Republic's okay

Supreme leader insists nuclear research is for peaceful purposes to produce energy; senior Iranian negotiator at Vienna talks says parties are 'closer than ever'

State Department spokesman says US in 'very final stages' of talks indirect talks with Islamic Republic aimed at salvaging the 2015 agreement

As Europe and US lose patience, Tehran believes it has scored points in Vienna by ensuring discussion of sanctions relief takes place in next round of talks

Britain, France and Germany call latest request from Tehran to pause talks 'disappointing;' UN nuclear chief casts 'doubt' on missing Iran data from cameras

European diplomats warn that Tehran is losing 'precious time,' deal could become an 'empty shell'; top Iranian negotiator accuses Europeans of playing blame game