World powers and Iran geared up Monday for fresh nuclear negotiations, with Russian President Vladimir Putin telling Iranian counterpart Hassan Rouhani he was upbeat about prospects for a landmark accord.
Speaking by phone two days before the talks resume in Geneva, Putin "stressed that a real chance has now emerged for finding a solution to this longstanding problem," the Kremlin said.
Rouhani, who has raised big hopes for an end to the decade-old standoff, told Putin that "excessive demands could complicate the process towards a win-win agreement," an Iranian government website said.
The comments came a day after French President Francois Hollande laid out in Israel the "essential" steps that Tehran must agree with the United States, China, Russia, Britain, France and Germany, known collectively as the P5+1 group.
These include stopping the enrichment of uranium to 20-percent purity, reducing enriched uranium stockpiles, and stopping construction of a new reactor at Arak, Hollande said.
It remains to be seen, however, whether the minor and reversible sanctions relief that the P5+1 is offering in return will be enough to persuade Tehran to play ball.
Iran's economy has been punished by a string of international sanctions. US and EU sanctions have more than halved its oil sales, sent the currency plummeting and inflation soaring.
One potential sticking point is Iran's previous demand the powers recognise it has a "right" to enrich uranium.
"No agreement will be reached without securing the rights of the Iranian nation," Iran's lead negotiator Abbas Araqchi said Sunday, predicting "difficult" talks.
Iran says it is enriching uranium to purities of up to five and 20 percent for civilian purposes. When further enriched to 90 percent, uranium can be used as fissile material in a nuclear bomb.
Iran's ability to enrich to 20 percent is of particular concern because this is most of the way to producing weapons-grade uranium.
Its stockpile is already large enough in theory to make several bombs.
At present, the UN atomic watchdog would detect any attempt to enrich to weapons-grade. But the fear is that soon this may no longer be the case as Iran adds to its 19,000 centrifuges, thus shortening its "breakout" time.
Another worry is the reactor being built at Arak, which theoretically could provide Iran with plutonium, an alternative to uranium in a bomb, although this is a longer-term concern.
Even though it would only be a "first phase" initial deal, an accord in Geneva would be a major breakthrough after a decade of rising tensions and failed diplomatic initiatives.
The International Atomic Energy Agency said last week that since Rouhani took office, Iran has put the brakes on expanding its programme.
But watching with a sceptical eye will be hardliners in both the United States and Iran, as well as Israel.
Any deal deemed too soft on Iran will make it harder for US President Barack Obama to dissuade Congress from passing more sanctions, which might scupper the negotiations.
Rouhani meanwhile risks losing the backing of supreme leader Ayatollah Ali Khamenei if the relative moderate's "charm offensive" since taking office fails to bear fruit soon.
"If Rouhani is not getting anywhere, the conservatives are going to make a strong comeback," Trita Parsi, author and president of the National Iranian American Council, told AFP.
The toughest to please could be Israel, which sees its very existence threatened by a nuclear-armed Iran allied with Hezbollah and Syrian President Bashar al-Assad.
Widely believed to have a formidable nuclear arsenal itself, Israel has refused to rule out bombing Iran's facilities, as it reportedly did with an Iraqi reactor in 1981 and a Syrian facility in 2007.
"Iran's dream deal is the world's nightmare," Israeli Prime Minister Benjamin Netanyahu said Sunday.
Hollande's trip to Israel was partly to try to ease Netanyahu's concerns. US Secretary of State John Kerry will do the same on Friday in his second visit in two weeks.
Netanyahu will also meet Putin in Moscow on Wednesday.
Russian Foreign Minister Sergei Lavrov made clear on Monday however that he felt some of Israel's concerns were "divorced from reality".