Iran minister floats nuclear talks extension
Iranian Foreign Minister Mohammad Javad Zarif has suggested that talks on Iran's nuclear programme could be extended beyond a 20 July deadline.
After two days of talks in Vienna, he said progress had been made and "more time may be useful and necessary".
Earlier, US Secretary of State John Kerry said there had been "tangible progress" but differences remained.
The talks aim to persuade Iran to limit its nuclear programme in exchange for the lifting of sanctions.
There has been growing speculation that the Sunday deadline for an agreement will need to be extended.
However, both Mr Zarif and Mr Kerry stressed that they still hoped to secure a deal by Sunday.
"I see an inclination on the part of my negotiating partners that they believe more time may be useful and necessary, but we haven't made that determination yet," Mr Zarif said after the current round of talks wound up on Tuesday.
"I have seen the readiness in the opposite side to listen. That's why this will open the path for a solution. Most of the text is ready. As soon as we agree on the key issues a final text can be reached in a few hours."
The talks in Vienna bring together Iran and the so-called P5+1 group, comprising the US, UK, France, China, Russia and Germany.
Mr Kerry said he was returning to Washington to discuss the prospects for an agreement with President Barack Obama and leaders in Congress.
He said those talks would include "the question of whether or not more time is warranted, based on the progress we have made and how things are going".
He added: "With respect to the issue of July 20, yes, that is still on the table. We are still working and we are going to continue to work."
An interim deal was reached last year. However, the parties have been unable to reach agreement on imposing long-term restrictions over Iran's uranium enrichment and plutonium production - processes that could yield material for nuclear warheads.
World powers suspect Iran is seeking atomic weapons. Iran strongly denies the charge, insisting that it is enriching uranium to fuel its power plants, and for medical needs.
A deal could see the lifting of oil and trade sanctions on Iran.