Vienna: US Secretary of State John Kerry and his Iranian counterpart went face to face again on Sunday with time running out to nail down a landmark nuclear deal in marathon talks in Vienna.
Ahead of Tuesday's final deadline, there were signs that inside the neoclassical palace-turned-hotel hosting the past nine days of talks in a hot Vienna that the end may be in sight.
The foreign ministers of France, Germany and Britain were expected back in the Austrian capital in the evening, followed possibly on Monday by their Russian and Chinese counterparts.
"Extending the talks is not an option for anyone... We are trying to finish the job," Iran's lead negotiator Abbas Araghchi told Iranian TV late Saturday, saying there was a "positive atmosphere".
But he added: "If we reach an agreement that respects our red lines then there will be a deal. Otherwise we prefer to return home to Tehran empty-handed."
One of the thorniest issues -- choreographing the complicated waltz of nuclear steps by Iran and reciprocal sanctions relief -- a compromise may be emerging, at least among experts thrashing out the complex final accord.
"There are still differences," an Iranian official insisted, however, while a Western diplomat said that on UN sanctions -- as opposed to EU and US ones -- there was "no agreement yet".
Under the mooted accord, building on a framework deal from April, a complex web of sanctions suffocating the Iranian economy will be progressively eased if Tehran massively scales down its nuclear programme for at least a decade.
This is aimed at extending the time needed by Iran to produce enough nuclear material for one bomb -- it denies any such aim -- to at least a year from several months at present.
Coupled with more stringent UN inspections, this will give ample time to stop any such "breakout" attempt, the powers believe, while keeping a modest civilian nuclear programme in place in Iran.