Arab Gulf states can expect a charm offensive from Iran when its moderate president-elect, Hassan Rouhani, a fluent Arabic speaker, takes office early next month.
The "diplomat sheikh", as he is nicknamed, has declared that his foreign-policy priority is to foster "friendly and close relations" with all Iran's neighbours, in particular Gulf countries and above all Saudi Arabia, a decades-long rival.
Any rapprochement between Tehran and Riyadh would ease soaring Sunni-Shiite sectarian tensions across the Middle East. A detente could also further a compromise solution to the civil war in Syria, which is in part a proxy conflict between Iran and Saudi Arabia.
It will not, however, be easy: the mistrust between the Gulf's two main powers is visceral, their differences are profound and hardliners in Tehran and Riyadh could try to derail any accommodation.
Gulf Arab states fear Iran's nuclear programme, while Iran and Saudi Arabia are on opposite sides of conflicts in Bahrain, Iraq, Lebanon and Syria.
The last is the most explosive. Saudi Arabia is funding and arming rebel Syrian Sunni forces battling to oust the president, Bashar Al Assad, while predominantly Shiite Iran is supporting his regime, a long-standing Tehran ally.
Yet because their differences are so profound, any rapprochement could also yield real dividends. "An understanding between Iran and Saudi Arabia is more decisive to the outcome in Syria than an understanding between the US and Russia," said Trita Parsi, who heads the National Iranian American Council, an advocacy group.
Mr Rouhani knows the Saudis well, having negotiated and signed the Islamic republic's first security agreement with the kingdom in 1998.
Iran and Saudi Arabia are not only neighbours but "brothers", he told a news conference on June 17, three days after his unexpected election triumph over hardline candidates. "We have very close relations, culturally, historically and regionally."
A day earlier, King Abdullah of Saudi Arabia congratulated Mr Rouhani on his victory and hailed his wish to improve relations.
Any renewed Saudi-Iranian relationship will face its biggest challenge over Syria. Riyadh has backed the opposition to Mr Al Assad politically, and with weapons.
The Islamic republic has provided advice, money and weapons to Damascus. Critical manpower to bolster Mr Assad's forces has come from Hizbollah, the Iranian-backed Lebanese Shiite movement.
The Iranian regime maintains that the US wants to topple the Syrian regime to weaken the Islamic republic. And Tehran views Saudi Arabia, Qatar and Turkey as US-backed proxies that are using the Syrian crisis to undermine Iran's regional role.
Still, there are possible points of cooperation.
Iran feels events in Syria are moving in its favour but Mr Rouhani realises Tehran must help to defuse the Syrian crisis if he is to repair ties with regional countries.
Better relations with Riyadh could help a key Iranian goal: to secure a seat at a peace conference on Syria to be convened in Geneva, possibly in September.
"Iran wants Syria stabilised for its regional standing and also for dealing with the West," said Mr Parsi, who sees Mr Rouhani's emphasis on Saudi Arabia as a major development. "Right now Iran feels it's in a position of strength because it feels Assad is going to survive."
But Tehran also knows its involvement in Syria is costly. Its backing of Mr Assad, and Hizbollah's involvement in Syria in particular, has infuriated Gulf Arab states and alienated the Palestinians, whose cause the Islamic republic has championed as a cornerstone of its 1979 revolution.
Iran's support for Mr Al Assad is also unpopular at home, where Iranians struggling to make ends meet resent squandering falling oil revenues on foreign causes.
Some experts doubt that Gulf states will respond to Mr Rouhani's overtures until Iran stops supporting the Assad regime or helps to end the Syrian civil war.
"And it's not just Syria. The Gulf states also see Iranian meddling in the eastern province of Saudi Arabia, in Bahrain, in Kuwait, in Yemen and in Iraq," said Gerald Butt, a London-based Gulf expert. "They'll want an overall change in Iranian policy before warming up to Tehran."
Others believe Tehran and Riyadh will have to sideline the Syrian question if they are to thaw their cold war. "It's way too optimistic to think that some type of Iran-Saudi reconciliation can open the door on Syria," said Scott Lucas, an Iran expert at Birmingham University in England.
"It's going to have to be more of an accommodation with the Gulf states despite Syria," he said. "Tehran and Riyadh still have a mutual interest in easing tensions no matter what's happening there."
Mahmoud Ahmadinejad, Iran's outgoing president, did little to reassure Gulf Arab states on any front. He portrayed the Saudis as US lackeys, and made a highly provocative trip last year to Abu Musa, one of three Iranian-occupied Gulf islands claimed by the UAE.
But Mr Rouhani has promised moderation in Iran's policies at home and abroad. Aside from vowing to repair relations with Gulf states, he has offered greater transparency on Iran's nuclear activities and declared a readiness for one-on-one talks with the US.
Mr Parsi believes that Mr Rouhani is well placed to ease regional tensions because he was endorsed by two influential former Iranian presidents: Akbar Hashemi Rafsanjani, a centrist, and Mohammad Khatami, a reformist.
"Each essentially masterminded and executed the rapprochement with Saudi Arabia in the mid-1990s," Mr Parsi said. "These are two men the Saudis respect and have some confidence in, whereas they had none in Ahmadinejad."
Even so, trust, could remain a stumbling block. Mr Rouhani personally is respected in the Gulf as a reliable interlocutor. But because he is not the only arbiter of politics in Tehran, many Gulf Arab officials worry that Iran's hardline supreme leader, Ayatollah Ali Khamenei, could act as a spoiler.
So any thaw between Tehran and Riyadh, if it comes, will be slow.
While Iran views the US as its greatest threat, Saudi Arabia reserves that distinction for the Islamic republic.
According to leaked US diplomatic cables from 2008, the Saudi king repeatedly urged Washington to destroy Iran's nuclear programme. Or, as the kingdom's ambassador to Washington put it: "He told you to cut off the head of the snake."
mtheodoulu@thenational.ae
edickinson@thenational.ae
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