Iranian Foreign Minister Mohammad Javad Zarif said Sunday that clinching a final nuclear deal with world powers was still possible, despite a tough latest round of talks in Vienna. Opportunity shouldn't be missed again like in 2005," Zarif wrote on Twitter, referring to Iran's long-stalled dispute with world powers over its nuclear programme. Iran and six world powers ended a fourth round of nuclear talks in the Austrian capital on Friday with "** tangible progress". Britain, China, France, Russia, the United States and Germany -- k**wn as the P5+1 group -- want Iran to radically scale back its nuclear activities, making any dash for an atomic bomb virtually impossible and easily detectable.