Intense negotiations were due to resume today between Iran and world powers, seeking a landmark breakthrough over Tehran's nuclear programme that also satisfies hardliners in Washington, Israel and the Islamic republic.
The talks come amid heightened Middle East tensions, with Iran's foreign minister accusing Israel of trying to "torpedo" the process after twin suicide bombings killed at least 23 people outside its embassy in Beirut yesterday.
Tehran's foreign ministry has blamed Israel and its "mercenaries".
Israel has denied the claims and its Prime Minister Benjamin Netanyahu was due to take his tireless campaign against a deal with Iran to Moscow today in talks with Russian President Vladimir Putin.
Iranian Foreign Minister Mohammad Javad Zarif was nonetheless upbeat about chances of a deal in Geneva, 10 days after talks between Iran and the United States, China, Russia, Britain, France and Germany -- the P5+1 -- failed to result in an accord.
"I think there is every possibility for success," Zarif, who also posted a conciliatory but defiant YouTube message online yesterday, said on a stopover in Rome.
But US President Barack Obama, fresh from seeking to dissuade lawmakers from imposing new sanctions on Iran, was more cautious: "I don't know if we will be able to close a deal this week or next week."
British Prime Minister David Cameron's office said yesterday after he also phoned Rouhani -- the first such contact in a decade -- that both leaders agreed it was "important to seize the opportunity".
The P5+1 powers want a "first phase" deal whereby Iran freezes the most sensitive parts of its nuclear activities while a long-term accord is hammered out.
But the question is whether Iran, seeking an easing of UN, US and EU sanctions that have more than halved the country's lifeblood oil exports, will accept what it is being offered in return.
On the table in Geneva is only a "limited, temporary, target and reversible" relief package that a senior US official said "will not come anywhere near helping Iran escape the hole that we've put them in."
"We will maintain the sanctions as long as we are not certain that Iran has definitively and irreversibly renounced its military programme to obtain nuclear weapons," French President Francois Hollande said in Israel on Monday.
