Three months after an interim agreement was reached, final negotiations for Iran's nuclear programme between Iran and six major powers are under way in Vienna.
This will be the most difficult stage yet. With days to go until the deadline, agreement has not been reached on major parts of the deal.
Key sticking points include Iran's refusal to grant international inspectors access to military sites.
One expert says if the talks fail, Iran and its rivals may enter dangerous territory.
Al Jazeera's Diplomatic Editor James Bays reports from Vienna, Austria.
Source: Al Jazeera