VIENNA • World powers raced yesterday to clinch a landmark deal to prevent Iran from acquiring a nuclear bomb, with a source close to the marathon talks saying an agreement was "98 per cent" completed.
The two sides intensified their diplomatic efforts ahead of a new deadline today to reach a deal to end a 13-year stand-off with the Islamic republic, which is seeking relief from crippling sanctions.
"I think we're getting to some real decisions. So I will say, because we have a few tough things to do, I remain hopeful. Hopeful," United States Secretary of State John Kerry told journalists in Vienna.
Mr Kerry, who took time out from the nuclear talks yesterday to attend a Latin Mass at St Stephen's Cathedral, described the latest talks with his Iranian counterpart Mohammad Javad Zarif as "positive".
European Union foreign policy chief Federica Mogherini tweeted that these were "decisive hours".
As the discussions entered a 16th day, there were glimmers of hope that a breakthrough might finally be in sight after the so-called P5+1 group - Britain, China, France, Germany, Russia and the US - talked deep into the night.
"Ninety-eight per cent of the text is finished," said a source close to the discussions, after a flurry of bilateral and multilateral meetings throughout Saturday.
Two or three key questions remained, however, including how long any agreement should last, and over the lifting of international sanctions on Iran such as a United Nations arms embargo, the source added. "Now there needs to be a political decision. And if that is taken, things could quickly" progress, the source said.
French Foreign Minister Laurent Fabius - who left for Paris yesterday but was due to return later - said on Saturday that the talks were approaching a critical moment.
"Everything is on the table. It's now time to decide," he said.
Three previous deadlines in this round of talks have been missed.
Under the parameters of a framework deal reached in Lausanne in April, Iran is to slash the number of its centrifuges from more than 19,000 to just over 6,000 and cut its stocks of enriched uranium, which can be used to make a bomb, from more than seven tonnes to about 350kg. The aim is to ensure that it would take Iran at least a year - from an estimated two to three months now - to acquire enough fissile material to build a bomb.
Negotiators left the thorniest issues until last, including a mechanism for lifting interlocking EU, US and UN sanctions.
A new hurdle was thrown up in recent days, with the Iranian delegation insisting that a UN arms embargo be lifted once a deal is reached.
The talks have also stumbled over demands to allow UN nuclear inspectors access to military sites to investigate suspicions that Iran had sought to develop nuclear weapons in the past. Teheran denies its nuclear programme has military aims.
A final agreement would be a diplomatic victory for US President Barack Obama, who has made the talks a centrepiece of his foreign policy, and for his Iranian counterpart Hassan Rouhani, a moderate seeking to end his country's diplomatic isolation.
Iran has for years faced UN, EU and US sanctions that have placed curbs on the country's oil and banking sectors, trade and everyday life for its population of 78 million.