Iran nuclear talks: Deadline extended to 7 July
Iran and six world powers have extended into next week their talks on finding a comprehensive agreement of Tehran's nuclear programme.
The deadline for reaching an agreement was 30 June, but all parties agreed to extend it by another week, to 7 July.
Russian Foreign Minister Sergei Lavrov said on Tuesday that a deal was now "within reach".
But US President Barack Obama has said he will still "walk away from the negotiations if... it's a bad deal".
And Iran's President Hassan Rouhani warned: "If the other side breaches the deal, we will go back to the old path, stronger than what they can imagine."
The so-called P5+1, which includes the US, UK, France, China and Russia plus Germany, want Iran to scale back its sensitive nuclear activities to ensure that it cannot build a nuclear weapon.
Iran, which wants international sanctions that have crippled its economy lifted in exchange, has always insisted that its nuclear work is peaceful.
The extension of the talks for a few days was widely expected, the BBC's Bethany Bell reports from Vienna, where the talks are being held.
She said differences on the key issues remained, including the timing of sanctions relief and the question of access for UN nuclear inspectors.
However diplomats say the sides are closer to a deal than they have ever been, she notes.
Iran's Foreign Minister Mohammad Javad Zarif returned to the talks on Tuesday, along with Atomic Energy Organisation of Iran (AEOI) chief Ali Akbar Salehi and Hossein Fereidoun, President Rouhani's younger brother and special adviser.
The presence of Mr Salehi was a sign of Iran's serious desire to accelerate the negotiations and achieve a comprehensive deal, Iran's state news agency Irna said.
On Monday, the US warned that a framework deal agreed in Switzerland in April had to remain the basis for a comprehensive agreement.
It followed a speech by Supreme Leader Ayatollah Ali Khamenei, who has the final say on all state matters, in which he rejected the key demands of the P5+1.
He insisted Iran would only dismantle its nuclear infrastructure if the sanctions were lifted first. He also ruled out a freeze on research and development for 10 years, as well as inspections of military sites.
In the US, President Obama has until 9 July to submit details of a final accord to Congress, triggering a 30-day review period before it can be signed and any US sanctions waived.
If a deal is submitted after 9 July, the review period will be doubled to 60 days.