The stakes are high but expectations low as Iran resumes talks today with world powers on its nuclear programme after a 14-month hiatus during which mutual mistrust became more corrosive and tensions steadily built.
Both sides, theoretically, have a keen interest in dialogue. Failure could trigger a countdown to a military confrontation neither wants.
"The atmosphere is bad," said Sir Richard Dalton, Britain's former ambassador to Tehran and a fellow at Chatham House, a leading British think tank. "And the situation is getting more dangerous."
There is time, however, for diplomacy. Technical problems, and apparent cyber sabotage, have disrupted Iran's drive to enrich uranium.
Both sides this past weekend struck a rare positive note on the eve of the two-day meeting in Geneva. Neither wants to be cast as spoiler.
The talks bring together Iran and the so-called P5+1, comprising the five permanent members of the UN Security Council - the US, Russia, China, France and Britain - and Germany.
Iran's president, Mahmoud Ahmadinejad, declared on Saturday: "We are ready to co-operate on a wide range of issues … This is a unique opportunity … that we hope the West will not waste."
In turn, the US secretary of state, Hillary Clinton, pledged the US is entering the talks in "good faith" and spoke of Iran's "right to have a peaceful nuclear programme".
Some in Tehran interpreted this as implicit acceptance of Iran's bottom line: that it has the right to continue enriching uranium on its own territory under international safeguards.
US officials maintained the West is entering the talks from a position of strength, claiming that global sanctions are hitting Iran hard.
Tehran, however, repeated its default position that it never negotiates under pressure.
Mutual mistrust runs deep. The West suspects Iran views talks as a means to ease international pressure and fears it will filibuster while pressing ahead with its nuclear activities. However, Mr Obama may be keen to give any re-engagement time, as the problems afflicting Iran's nuclear programme allow breathing space.
Tehran, in turn, suspects the West is going through the diplomatic motions while it waits for the pain of sanctions to force Iran to compromise and, if that fails, to prepare for military action against Iranian nuclear facilities.
Inauspiciously, it took Iran and the P5+1 four months just to thrash out agreement on a time and place to meet. And an agenda has yet to be set. Establishing one will be the primary aim of the Geneva talks - but even that could prove a hurdle too high. Iran insists it will not discuss its uranium enrichment programme. It instead wants a wider discussion on regional security issues, global economic problems, and Israel's undeclared stockpile of nuclear weapons.
But Iran's nuclear programme is the P5+1's focus of concern.
"The participants will probably measure success by whether there's an agreement to meet again with a formula that allows for a discussion of the important points for both sides," Mr Dalton said in a telephone interview.
The atmosphere has soured badly in recent days and weeks. Iran has accused the West of bad faith by using "hideous" tactics - from sanctions and cyberwarfare to murder - to weaken its negotiating position.
Tehran blamed the intelligence agencies of the US, Britain and Israel for the assassination last Monday of one of its nuclear scientists.
The disclosures by the whistle-blowing website, WikiLeaks, also have stirred the unpredictable mix. Supposedly confidential US diplomatic cables showed that many Arab leaders privately share the West's concerns that Iran's nuclear programme is secretly aimed at weapons development.
Tehran insists its atomic activities are solely to generate electricity for domestic supply, freeing oil for export.
Adding to the dispute, Iran yesterday said it had produced a first batch of uranium yellowcake, the raw material for nuclear enrichment, The Associated Press reported.
Some experts believe the unauthorised WikiLeaks disclosures could strengthen the P5+1's hand because they demonstrate Iran's isolation in a region where it wants acknowledgment as a leading player. But WikiLeaks also revealed that Barack Obama, the US president, who came to power with promises to engage Iran had, from the start, simultaneously pursued an alternative strategy of pressuring Tehran because he had little faith that dialogue would succeed.
This gives Iran ammunition to claim its interlocutors were never serious about reaching a compromise. In turn, this now may prompt Washington to prove otherwise, said Farideh Farhi, a renowned Iranian analyst at the University of Hawaii.
Adding to the uncertainty are divisions within both Tehran and Washington. Infighting between Tehran's fractious leadership last year scuppered a key confidence-building measure on Iran's nuclear programme that required Tehran to send abroad the bulk of its stockpile of low-enriched uranium.
At the same time, the rise of a Republican majority in the House of Representatives could pressure Mr Obama's administration to harden its stance on Iran, making a deal more difficult.
Despite Mr Obama's disinclination to use force against Iran, the geopolitical realities of the region have not changed much since the Bush years, said Dr Trita Parsi of the Woodrow Wilson Centre.
"The choice is now between trying diplomacy in earnest or prepare for the confrontation that inevitably will come if the current trajectory of tensions prevail."