High-level negotiations on Iran’s nuclear programme enter their last day on Tuesday before a deadline for agreeing the outline for a comprehensive settlement, with top diplomats still struggling to overcome persistent obstacles. 
 
 The US secretary of state, John Kerry, his Iranian opposite number, Mohammad Javad Zarif, alongside foreign ministers from France, the UK, Germany and China, worked late into the evening on two consecutive nights in an effort to break the deadlock. 
 
 Russia’s Sergei Lavrov left the talks on Monday afternoon to hold official meetings in Moscow, but said he would return to Lausanne later on Tuesday, telling reporters in the Russian capital that there was a good chance of success. 
 
 “The chances are high. They are probably not 100% but you can never be 100% certain of anything. The odds are quite ‘doable’ if none of the parties raise the stakes at the last minute,” Lavrov said on Tuesday. 
 
 A US State Department spokeswoman said on Monday night that prospects of a deal on Tuesday were “50-50”. Working teams of experts and diplomats were instructed to work through the night on outstanding issues in the search for a breakthrough. 
 
 
 
 Diplomats said that the principal sticking point was the issue of UN security council sanctions on Iran. Zarif’s team is sticking by the demand by their country’s supreme leader, Ali Khamenei, for all sanctions to be lifted at once in return for Iranian acceptance of restrictions on its nuclear programme over a period of at least 10 years. 
 
 
 
 The six-nation group is offering several relief measures, lifting the EU oil embargo and removing banking restrictions in moves synchronised with the suspension of corresponding US sanctions. But it insists that some UN sanctions must stay in place until Iran has convinced the international community it has no intention of pursuing a weapons programme, a task that could take many years. 
 
 European diplomats said the final day of talks would show whether Iran’s seemingly immovable stance on UN sanctions was a hardball negotiating tactic, or whether Khamenei had left them no negotiating space. Khamenei said on his website on Monday morning: “Sanctions must be lifted in one go, not as a result of future Iranian actions.” 
 
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 In a further sign of problems at the talks, Khamenei’s foreign policy adviser, Ali Akbar Velayati, cast doubt on the west’s motives at the talks. 
 
 
 
 “Our negotiating team are trustworthy and compassionate officials that are working hard, but they should be careful with the enemies’ deceptive and skilful tactics,” Velayati told Fars news agency. 
 
 A diplomat in Lausanne quoted by the Chinese news agency Xinhua said the atmosphere on Monday had turned from optimism to gloom among negotiators. 
 
 Another longstanding hurdle to an agreement, the question of Iranian research and development, has been partially resolved. Iran has accepted strict limits on its development of new super-efficient centrifuges during the first 10 years of a deal, but there are disagreements on what would happen afterwards. 
 
 
 
 The six-nation group wants restrictions to extend for a further five years, wary that new centrifuges could drastically reduce Iran’s breakout time (the period it would need to build a bomb, should it make that decision). Iran rejects such prolonged curbs on its centrifuge development, saying it would render the country dependent on foreign technology. 
 
 A third problem seems to have been largely resolved in the past few days. Iran wanted to keep some centrifuges spinning at its underground enrichment plant in Fordow. The six powers negotiating with Tehran proposed a compromise in which a few hundred centrifuges spin but do not process uranium. They would purify other elements used for medical and scientific purposes. 
 
 Reza Marashi, research director of the National Iranian American Council, said even if the 31 March deadline was missed, none of the parties at the table would walk away. 
 
 “Both sides stand to lose massively. There is a propensity to focus on minutiae, but what has got lost is how much each side has to lose,” Marashi said. “Are we going to let this collapse over differences on how long Iran isn’t allowed to work on new centrifuges?” ||||| With just six days before the deadline, Iran's nuclear talks seem to be faltering as U.S. Secretary of State John Kerry arrived in Vienna on Sunday. 
 
 Kerry had his work cut out for him. As he worked to mend ties with Germany in its espionage dispute with the U.S. and handle the ongoing crisis in Israel and Gaza, Kerry also took on face-to-face meetings with his Iranian counterpart Mohammad Javad Zarif with a ticking clock behind them. By the day's end, no breakthrough had been produced and representatives from the six countries negotiating with Iran said that big hurdles remained. 
 
 The expiration of the interim deal 
 
 After decades of tense relations and mistrust, Iran and the United States (as part of the P5+1 Group) surprised the world by managing to secure an interim deal last fall that would ease sanctions on the Islamic Republic in exchange for suspending work on its nuclear program. July 20 was the date set for the deal to expire. And here we are. 
 
 While there have been some slight hints that discussions could extend beyond the deadline, the P5+1 group seems keen on getting a deal done by July 20. 
 
 As the Associated Press noted: 
 
 Lower-ranking officials represented both Russia and China, possibly reflecting their view even before Sunday that talks past July 20 are unavoidable. But Iranian Deputy Foreign Minister Abbas Araghchi suggested any extension would be relatively short, saying "there is not much willingness" by either side to go a full six months. He, too, earlier spoke of "huge and deep differences." 
 
 "There is a huge gap" 
 
 As reported, several gaps remain between the six countries and Iran, including major questions about the level to which Iran can enrich its uranium. Today, things got interesting. 
 
 Word started to spread about a speech given several thousand miles east of Vienna, in which Iran's Supreme Leader Ayatollah Ali Khamenei emphasized the need for Iran to enrich its uranium capacity at the very moment that the Iranian nuclear delegation and the P5+1 Group were bargaining to reduce it. 
 
 As the news broke, the words "scuttle" and "undermine" began floating: 
 
 Basically looks like Khamenei cut Zarif and co at the knees: http://t.co/9CMVgKD6dX — Jordan Hirsch (@jordanchirsch) July 14, 2014 
 
 Classic Khamenei: 1) Express support for negotiations 2) Undermine negotiators by setting impossible red lines. http://t.co/7dhb5BIzO9 — Karim Sadjadpour (@ksadjadpour) July 14, 2014 
 
 Does Iran want a deal? 
 
 Are these negotiating tactics or reluctance? As Gerald Seib points out (paywall), while the U.S.-led sanctions imposed by the international community had a pretty devastating bite, all the jockeying in Vienna is for naught if Iran doesn't want a deal: 
 
 But there is a difference between wanting a deal and considering one essential. Would economic relief be simply convenient, or does Iran consider failure to achieve it an existential threat to the regime? The negotiations won't succeed unless Iran wants a deal more than its international interlocutors do. And there's probably no way to know for sure exactly how much urgency Iran attaches to a deal until talks reach their 11th hour. 
 
 We'll find out soon enough. ||||| Image copyright Reuters Image caption The sides are carrying on talking after having missed several self-imposed deadlines 
 
 Iran's foreign minister has accused world powers of making it harder to reach agreement at nuclear talks in Vienna by taking different positions. 
 
 Mohammad Javad Zarif said "several countries" were also making "excessive demands". His UK counterpart said the process was proving "painfully slow". 
 
 The so-called P5+1 - US, UK, Russia, France, China and Germany - said talks would go on until at least Monday. 
 
 The powers suspect Iran of seeking nuclear weapons, which Iran denies. 
 
 Iran says its nuclear programme is for purely peaceful purposes. 
 
 The sides have been holding marathon negotiations to reach a long-term agreement and have missed successive self-imposed deadlines. 
 
 Both Mr Zarif and US Secretary of State John Kerry said though that they would not be rushed into making a deal. 
 
 "We're here because we believe we are making real progress," John Kerry told reporters on Thursday. 
 
 But he cautioned that "we are not going to sit at the negotiating table forever" and that he was prepared to "call an end" to nuclear talks with Iran if "tough decisions" are not made." 
 
 Media playback is unsupported on your device Media caption Iranians describe how they hope life will become more affordable if sanctions are lifted. 
 
 The failure to reach a deal by Friday means the US Congress will now take twice as long - 60 days - to decide whether to accept or reject any eventual deal, keeping sanctions in place until then. 
 
 Mr Zarif said late on Thursday that the negotiating position of the P5+1 was making it harder to reach a deal. 
 
 "Unfortunately we have seen changes in the position and excessive demands... by several countries," he said. 
 
 The sides have continued talking long past a self-imposed 30 June deadline to turn a framework deal into a comprehensive, final agreement. 
 
 Media playback is unsupported on your device Media caption Iran has the world's fourth largest crude oil reserves: 150 billion barrels 
 
 The P5+1 and Iran are working on a deal which will curb Iran's nuclear programme in return for sanctions relief, though the pace of the lifting of sanctions has been a major sticking point. 
 
 Analysis: BBC's Lyse Doucet, Vienna 
 
 Another deadline was missed - but no side in this marathon is calling it a bad sign. Negotiators emphasise how far they have come, how close they are. 
 
 But at this 11th hour there are, unsurprisingly, conflicting views on the impasse. Western diplomats speak of a small number of political and technical issues to resolve and place the onus on Iran. 
 
 But a senior Iranian official lamented that Iran now feels it is in five bilateral negotiations since every country has different "red lines." A senior Iranian official would only speak "of certain changes in the US position" as well as "a walking back" by other countries - they deny that. 
 
 It is clear more time is needed - but how much is not clear to anyone. An Iranian official said this wasn't "the 11th hour, but 13th or 14th". This is a process which, from the start, has had a clock all its own. 
 
 The P5+1 and Iran are still believed to differ in three key areas - international inspections of Iran's non-nuclear sites, sanctions relief, and how Iran's compliance will be verified. 
 
 Iran also wants a UN Security Council arms embargo to be scrapped - something the US has ruled out.
– With a midnight deadline looming, Iran and the six nations it's conferring with in Switzerland have reached a deal—to continue talks for a deal on Tehran's hotly contested nuke program. The nations are expected to release a joint statement today announcing they'll enter a "new phase" of negotiations that will end with a full-fledged agreement by the end of June, according to two unnamed officials, per the AP. While headway had been made, key sticking points mean the language is being revised to say today's talks will end in an "understanding," with "technical" issues to be resolved in coming months, the AP notes. What's going on: Iran wants all UN sanctions lifted immediately; the six-country bloc is willing to make other concessions—including nixing banking limitations and getting rid of the EU oil embargo—but wants some sanctions in place until Iran makes good on its promises. That looks unlikely, with supreme leader Ali Khamenei posting yesterday, "Sanctions must be lifted in one go, not as a result of future Iranian actions," per the Guardian. Although Iran has said it will acquiesce to restrictions on its centrifuge development over the next decade, beyond that is fair game. The other countries at the negotiating table want to cut down Iran's "breakout time" (the time it would take to construct a bomb) by adding five more years onto the 10-year moratorium. Iran argues that would keep the country under the thumb of other nations' technology, the Guardian notes. The question of Iran's uranium stash remains on the table, with Tehran's main negotiator saying Iran has no intention of shipping its fuel out, and the US State Department conceding that there's still a lot of back and forth on this issue. "The bottom line is that we don't have agreement with the Iranians on the stockpile issue," a State rep said yesterday, per the New York Times.