An accord to curb Iran's nuclear programme remains elusive due to disagreements on fundamental issues, France's foreign minister said on Saturday in Vienna, just days before the June 30 deadline for a deal.
Laurent Fabius spoke to reporters upon arrival in the Austrian capital after top US and Iranian diplomats said hard work was still needed for what could be their final negotiations to bridge significant differences.
"What we want is a robust deal that recognises Iran's right to civil nuclear power, but guarantees that Iran gives up definitively the nuclear weapon," Fabius said.
For this there were three "indispensable" conditions, he said: A lasting limitation of Iran's research and development capacity, rigorous inspections of sites, including military if needed, and the automatic return of sanctions if Iran violates its commitments.
"These three conditions respect Iran's sovereignty. They have still not been accepted by everybody, yet they form the key base of the triangle that forms the robust agreement that we want," he said.
The self-imposed deadline for a deal under which Iran would cut back its nuclear programme in exchange for relief from economic sanctions, expires on Tuesday.
"We have a lot of hard work to do. We have some very tough issues," US Secretary of State John Kerry said according to a State Department draft transcript.
"I agree. Maybe not on the issues. But on the fact that we need to work really hard in order to be able to make progress and move forward," Iranian Foreign Minister Mohammad Javad Zarif was cited as saying in the transcript.
Nonetheless, Kerry also said he was "hopeful" of a successful outcome. His meeting with Zarif ended after 90 minutes.
The main differences are on the pace and timing of sanctions relief for Iran in return for its steps to restrain its nuclear programme and on the nature of monitoring mechanisms to ensure Tehran does not cheat on any agreement.
US and European negotiators also want to ensure there is a mechanism for restoring US, European Union and United Nations sanctions if Tehran fails to meet its commitments under any future accord aimed at ending a 12-year nuclear standoff between Iran and the West.
The United States, Israel and some Western nations fear that Iran has been trying to develop a nuclear weapons capability but Tehran says its programme is for peaceful purposes only.
In addition to Iran and the United States, the talks include Britain, China, France, Germany and Russia. Foreign ministers from all the nations, as well as the EU foreign policy chief, are expected in Vienna in the coming days.
In November, the seven nations involved in the talks set a late March deadline for a framework agreement, which they ultimately reached on April 2, and a June 30 deadline for a comprehensive deal.
The real deadline is not June 30 but July 9, diplomats say.
The US delegation must present the deal to Congress by July 9 if a mandatory congressional review period before President Barack Obama can begin suspending sanctions is to be limited to 30 days. After July 9, the review will last 60 days, according to a law passed recently by US legislators.
Negotiators involved in the talks fear that such a lengthy delay, which would also hold up the cancellation of United Nations nuclear-related sanctions by the UN Security Council, would be too long and would create the opportunity for any deal agreed in Vienna to unravel.