US Secretary of State John Kerry and his Iranian counterpart laid the groundwork Tuesday for the possible extension of a Sunday deadline to strike a historic nuclear deal after intense talks in Vienna.
Both Kerry and Mohammad Javad Zarif said however after two days of one-on-one discussions which failed to yield any major breakthrough that negotiators would still keep trying until the July 20 cut-off.
After a decade of rising tensions, such an accord between Iran and the five permanent members of the UN Security Council plus Germany is aimed to easing concerns that Iran might develop nuclear weapons and silencing talk of war.
"I am returning to Washington today to consult with President (Barack) Obama and with leaders in Congress over the coming days about the prospects for a comprehensive agreement, as well as a path forward if we do not achieve one by the 20th of July, including the question of whether or not more time is warranted, based on the progress we've made and how things are going," Kerry said.
He told a news conference that there had been "tangible progress on key issues, and we had extensive conversations in which we moved on certain things", although "very real gaps" persisted between the two sides.
Zarif, in a separate news conference, said that although he still hopes a deal would be possible by Sunday, he believed enough progress has been made to justify a continuation.
"As we stand now, we have made enough headway to be able to tell our political bosses that this is a process worth continuing," Zarif said. "This is my recommendation. I am sure Secretary Kerry will make the same recommendation."
An interim accord struck in November between Iran and the five permanent members of the UN Security Council plus Germany expires on July 20.
Extending the deadline has always been a possibility in order to keep the parties talking, but Washington in particular has stressed it will not agree to such a move without key concessions from Iran first.
- Mission not accomplished -
Iran denies seeking the atomic bomb and wants the lifting of crippling UN and Western sanctions.
The six powers want Iran to dramatically reduce in scope its nuclear programme for a lengthy period of time and agree to more intrusive UN inspections.
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This would greatly expand the time needed for the Islamic republic to develop a nuclear weapon, should it choose to do so, while giving the world ample warning of any such "breakout" push.
Iran on the other hand has stated it wants to expand its nuclear facilities, insisting they are for purely peaceful purposes and that it has the perfect right to nuclear activities under international treaties.
Both sides are also under intense pressure from hardliners at home -- midterm US elections are due in November -- and both are wary of giving too much away after several months of talks.
- 'Innovative proposal' -
Kerry, along with the foreign ministers of France, Germany and Britain and the deputy foreign minister of China jetted into the Austrian capital on Sunday seeking to inject some momentum to the negotiations.
But the three European ministers left on Sunday evening empty-handed, leaving Kerry to keep trying.
Britain's now former foreign secretary William Hague had said a "huge gap" remained on the key issue of uranium enrichment.
This activity can produce fuel for the country's sole nuclear plant or, if further enriched, the material for an atomic bomb.
Israel, the Middle East's sole if undeclared nuclear armed state and which together with Washington has refused to rule out military action, is opposed to any enrichment by Iran at all.
Zarif however outlined a possible compromise in an interview with the New York Times published on Tuesday.
This "innovative proposal" would see Iran essentially freeze its enrichment capacities at current levels for between three and seven years.
Kerry stuck to his guns on Tuesday, saying that nothing short of a reduction in Iran's enrichment capacities was acceptable.
"We have made it crystal clear that the 19,000 (centrifuge enrichment machines) that are currently part of their programme is too many," Kerry said.
A senior US official said last week the programme should be limited for a "double digit" number of years.