Moscow - World powers resume crisis talks with Iran on Monday in hopes that a crippling oil embargo will finally force the Islamic Republic to scale back its nuclear drive.
The two-day meeting follows a bruising May session in Baghdad during which Iran nearly walked out of negotiations aimed ultimately at keeping it from joining the exclusive club of nations with an atomic bomb.
Host Russia however is keen to flex its diplomatic muscle and make Iran an example of how Moscow's influence over Soviet-era partners could be used to avoid foreign military intervention in the 16-month crisis raging in Syria.
"There are reasons to believe that the next step will be taken in Moscow," Russia's Deputy Foreign Sergei Ryabkov said on Friday. "It is important for Russia to ensure that the negotiating process continues."
Failure in Moscow could leave the process in tatters and raise the threat of air raids from arch-foe Israel - a fateful scenario in which broader conflict would lead to a spike in oil prices that could tip over the world's teetering economy.
But a July 1 deadline for a full EU oil embargo and the June 28 rollout of US sanctions against a host of Iranian oil clients is providing added incentive for Tehran to bargain more seriously.
Two of the biggest bones of contention involve the speed with which world powers lift existing sanctions and the recognition of Iran's "right to enrich".
The latter is emerging as a key demand that Iranian negotiator Saeed Jalili is likely to present to Catherine Ashton, the EU foreign policy chief who represents the five permanent UN Security Council members and Germany at the talks.
"We expect that Iran's right to nuclear technologies, including uranium enrichment, will be recognised and respected," Jalili told Russia's RT state-run world news channel in comments translated from Farsi.
Iran for its part "has the capacities to cooperate in disarmament and nuclear non-proliferation, so these capacities should be used by the international community," Jalili said in Friday's broadcast.
"I think that addressing these two issues will help to advance the negotiations."
Iranian President Mahmoud Ahmadinejad told a German Sunday paper that his country was ready to take a "positive step if the other party makes a similar step" at the talks.
EU officials say Iran has agreed to discuss the idea of limits to its enrichment programme under a proposal initially outlined in Baghdad.
The deal would see the Islamic Republic stop enriching uranium to 20% - seen as being just steps away from weapons-grade - and ship out its existing stock while also shuttering its forbidden Fordo bunker.
The tough terms would not lead to the quick lifting of sanctions but instead see the West extend some forms of peaceful nuclear energy cooperation and provide assistance for Iran's battered aircraft industry.
Europe would also help Iran export oil to key client Asia by easing an EU ban on tanker insurance.
Iran has previously scoffed at the idea of accepting only reactor fuel and civil aviation parts in immediate return.
But pressure is mounting on US President Barack Obama from both Israel and the US Congress ahead of his November re-election bid to reject any compromise.
A bipartisan letter signed by 44 Senators urged Obama on Friday to cut off negotiations unless Iran agrees to shutter the Fordo bunker and limit uranium while shipping out all material of higher grade.
The Iranian delegation headed by Jalili and including his deputy Ali Bagheri along as well as Deputy Foreign Minister Abbas Araghchi arrived in Moscow early on Sunday.