Talks between world powers and Iran on a comprehensive nuclear agreement will continue past Tuesday’s deadline, the EU’s foreign policy chief says.
Federica Mogherini told reporters in Vienna that the negotiations would carry on “for the next couple of days”.
Meetings took place late into Monday night, with foreign ministers grappling to resolve outstanding issues and warning a deal was not yet assured.
The talks have intensified since the previous deadline was missed last week.
The so-called P5+1 – 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 crippling international sanctions lifted, has always insisted that its nuclear work is peaceful.
Representatives of both sides said a deal was closer than ever before as foreign ministers arrived at Vienna’s Palais Coburg hotel on Monday. But when the talks broke up in the early hours of Tuesday, it seemed likely that the midnight (22:00 GMT) deadline would be missed.
Ms Mogherini said the negotiations, which she has been chairing, would continue but insisted: “This does not mean we are extending our deadline.”
“We are interpreting in a flexible way our deadline, which means that we are taking the time, the days we still need, to finalise the agreement,” she added.
The Italian diplomat said that a deal was “something which is still possible even if we are now getting into the difficult time”, with several issues to resolve.
A spokesman for the Iranian delegation told the AFP news agency it had “no deadline”.
US Secretary of State John Kerry had wanted an agreement finalised by Wednesday at the latest so that it could be submitted to the US Congress for approval by Thursday. If a deal is presented later, the review period will double from 30 days to 60.
Russian Foreign Minister Sergei Lavrov said “very significant progress” had been made at the talks.
“We singled out eight or nine issues, fewer than 10, where we need to add the finishing touches,” Russian state news agency RIA Novosti quoted him as saying.
Mr Lavrov believed a long-term accord could be ready “in a few days”.
“Everyone’s focused on securing good-quality agreements. And there is every reason to believe that we’ll achieve that,” he said, according to the Interfax news agency.
The sticking points are said to include the duration of limits on Iranian nuclear research and development, guidelines for international inspections and how sanctions will be lifted.
Tehran is also demanding that the UN ban on the import and export of conventional arms and ballistic missiles be lifted as part of any deal.
The text of a new UN Security Council resolution is being drafted, but the US and its European allies oppose lifting the arms embargo because Iran has been accused of fomenting unrest in the Middle East.
Russia and China have expressed support for lifting the embargo, which was imposed in 2007.
Officials from the global nuclear watchdog, the International Atomic Energy Agency (IAEA), meanwhile held “intense discussions” with officials in Tehran on Monday in an effort to resolve questions about the possible military dimensions of Iran’s nuclear programme.