Powers warn Iran ‘now is the time’ for nuclear deal

“The time is now… We are very close,” said Mogherini, adding the atmosphere was “constructive, positive.”

On one of the thorniest issues — choreographing the nuclear steps to be taken by Iran in exchange for reciprocal sanctions relief — a compromise may be emerging.

The deal between Iran and the P5+1 would end a standoff dating back to 2002 when dissidents first revealed undeclared nuclear facilities in Iran.

Officials have stressed all week that this is the endgame, and after missing several deadlines they are not planning to extend the negotiations again.

“I hope that it is clear to all parties in these final days that this is a unique chance that we have now,” said German Foreign Minister Frank-Walter Steinmeier as he arrived back in Vienna.

“We have a wonderful chance after 12 years of talks finally to end a long-running conflict… which would also send out a signal for the whole region.”

Russian Foreign Minister Sergei Lavrov also arrived back in the city, his ministry tweeted.

A deal would also hold out the promise of bringing Iran back into the diplomatic fold at a time of mounting unrest in the Middle East.

Zarif said in an English YouTube message that an accord could “open new horizons to address important common challenges”, referring to the “growing menace of violent extremism and outright barbarism,” an implicit statement on the Islamic State (IS) militant group.

On Saturday it appeared that another stumbling block to the deal — a stalled UN probe into allegations of past efforts by Iran to develop the bomb — may potentially be close to being resolved too.

Senior officials from the International Atomic Energy Agency (IAEA) were flying out to Iran, just days after last week’s visit by the UN watchdog’s chief Yukiya Amano.

“I think it would be very difficult to imagine Secretary Kerry at this point walking away, this close to the finish line,” Iran expert Suzanne Maloney from the Brookings Institution told AFP.

“I just don’t think there’s any real likelihood that this collapses.”