Rollercoaster talks aimed at stopping Iran getting a nuclear bomb went into extra time on Wednesday amid cautious signs that after seven days of tough negotiations a framework deal may be near.
Speaking after Iran and major powers missed a midnight deadline to agree the outlines of a potentially historic accord, Iran's chief negotiator appeared hopeful.
"We believe that at the end of the day we will be able to come to a conclusion and a resolution for all issues," Abbas Araghchi said in a live interview with Iranian state television from Lausanne.
He said he expected a press statement to be released, but repeated that global powers and Iran were still haggling over two main sticking points -- a mechanism for lifting crippling sanctions against the Islamic republic and the country's research ands development programme.
The US, Russia, China, Britain, France and Germany want Iran to scale down Iran's nuclear programme to extend the "breakout" time needed for Iran to assemble enough nuclear material to make a bomb.
German Chancellor Angela Merkel said she hoped "that we will reach a compromise today which meets the conditions we have laid down, which means Iran has no access to a nuclear weapon."
Iran denies wanting the bomb and its negotiators are under strict orders from supreme leader Ayatollah Ali Khamenei to refuse any curtailing of its programme without sanctions relief.
Araghchi offered some specifics, saying "in the first step of the deal, we are eager for all sanctions including economic, financial, oil and bank" to be lifted.
Global powers have always refused an immediate lifting of all sanctions in order to be able to swiftly put them back into place if Iran violates the deal.
The stakes are high, with fears that failure may set the United States and Israel on a road to military action to thwart Iran's nuclear drive.
The White House warned again Tuesday that the military option to deprive the Islamic republic of nuclear arms remained "on the table".
- Contradictory signals -
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Russian Foreign Minister Sergei Lavrov had raised hopes in the early hours Wednesday of "an agreement in principle on all key aspects of the final settlement".
But a senior US State Department official said tersely: "All issues have not been agreed."
An "optimistic" British Foreign Secretary Philip Hammond said Wednesday a "broad framework of understanding" had been reached, but he also said there were "some key issues that have to be worked through".
Coming away from Lausanne with a deal meant "the Iranians being willing to meet us where there are still issues to deal with," Hammond told British media.
Hawkish French Foreign Minister Laurent Fabius, who along with Lavrov and China's Wang Yi have now left the talks, said progress so far was "not enough".
Kerry, who on Wednesday went into his first bilateral meeting with his Iranian counterpart Mohammad Javad Zarif in several days, overnight briefed US President Barack Obama and his national security team on the negotiations by secure video conference.
If the outlines under negotiation fall short of firm commitments by Iran, Obama could find it hard to fend off attempts by his Republican opponents to pass fresh sanctions on Tehran.
Iran's negotiators are also under pressure from domestic hardliners not to give too much away while also delivering on President Hassan Rouhani's promise to win the lifting of sanctions.
US Republicans fear that Iran will still be able to get the bomb -- a concern shared by Israeli Prime Minister Benjamin Netanyahu, whose country is widely assumed to have nuclear weapons itself.
Netanyahu, in his fourth broadside in as many days, warned Wednesday against a bad deal that would "endanger Israel, and the Middle East and the peace of the world."
Some areas of the mooted deal, including the future size of Iran's uranium enrichment capacity, appear to have been tentatively sewn up.
But the two sides still appear to be discussing other areas, including sanctions relief, what to do with Iran's stockpiles of nuclear material, and how long the deal should last.