** FILE ** Saudi Arabia's King Fahd right, talks with U. S. president Bill Clinton in this undated file photo. Saudi Arabia's King Fahd, who moved his country closer to the United States but ruled the world's largest oil producing nation in name only since suffering a stroke in 1995, died early Monday Aug. 1, 2005, the Saudi royal court said. He was said to be 84. (AP Photo/ Saudi Gazette)

At his first press conference after getting elected, Iranian President Hassan Rouhani singled out Saudi Arabia as the country his government would try particularly hard to build friendly relations with. He even referred to Saudis as Iran's "brothers."

Things didn't turn out quite as Rouhani had hoped. Middle Eastern geopolitics have changed dramatically since the mid-1990s, when Rouhani had helped engineer a Saudi-Iran rapprochement. The Iraq war had caused Saudi to lose both faith in American intentions and competence. The Arab Spring -- and what the Saudis viewed as the betrayal of Egypt's Hosni Mubarak by the U.S. -- convinced Riyadh that Washington would no longer uphold its promise to secure and protect pro-Western Arab dictators.

Moreover, by refraining from using military force against Syrian President Bashar Assad, America had proved that its desire to avoid new wars in the Middle East superseded its hegemonic obligations to uphold security and stability in region. It looks to the Saudis like America has simply abandoned its ally.

The U.S.-led order for the region established in the 1990s was bound to collapse.

Moreover, Saudi oil has lost its lure. The U.S. has significantly increased its own oil production and reduced its dependence on Saudi oil. And as a result of the Iran nuclear deal -- which Saudi Arabia vehemently opposed -- Iranian oil will soon return to the world markets. Many states are planning to reduce their dependency on Saudi oil by shifting some of their consumption towards Iranian crude.

And then of course, Iran is no longer checked geopolitically by Saddam Hussein in Iraq and the Taliban government in Afghanistan. Add to that the lifting of sanctions on Iran -- which "may be days away" according to U.S. Secretary of State John Kerry -- and it becomes clear why Riyadh fears that its geopolitical decline will be exacerbated by Iran's ascendancy.

Despite this dramatically altered geopolitical map, the Rouhani government did attempt to mend fences with Saudi Arabia. Rouhani appointed Admiral Ali Shamkhani as the secretary of the Supreme National Security Council -- Iran's equivalent of national security advisor. Shamkhani, who is ethnically Arab, received Saudi Arabia's highest medal in 2004, the Order of Abdulaziz Al Saud, for his efforts to improve relations with the Arab states of the Persian Gulf. The thinking appears to have been -- at least in part -- that Shamkhani was the best suited official to orchestrate Iranian outreach to Saudi.

American order was based on the exclusion of two of the region's most powerful states -- Iran and Iraq -- and could only be sustained as long as the U.S. was willing to pay for it through its own blood and treasure.

Furthermore, Iran's Foreign Minister Javad Zarif declared his willingness to travel to Riyadh but didn't receive an invitation until King Abdullah bin Abdulaziz Al Saud died in January 2015. Zarif attended the king's funeral but no Saudi official agreed to meet with him during his visit. Months earlier, Zarif did have a brief sit-down with the then-foreign minister in New York, the late Prince Saud al-Faisal, but in retrospect it is clear that very little was achieved.

Part of Iran's problem in dealing with Saudi Arabia is Riyadh's inherent sense of insecurity, rooted in its dependence on the U.S. and the outsourcing of its security to Washington. As Iranian academic Nasser Hadian points out, Saudi Arabia outspends Iran on arms by a factor of six. Its military has the most modern American weaponry. It is the key state in the Gulf Cooperation Council -- a body that was created to balance Iran's power.

Thus, Iran's power or military capabilities cannot explain Saudi Arabia's sense of insecurity. Rather, Hadian argues, Saudi's sense of vulnerability is inherent in the very political nature of the Saudi regime -- the fact that it is renting its security from the U.S. (which, incidentally, is increasingly reluctant to provide that protection). A tenant will never enjoy the same sense of security as a homeowner, so to say. This leaves Iran with limited options, as there is little Tehran can do to alleviate Saudi Arabia from this innate uncertainty, Hadian maintains.

Kerry discusses a long-term nuclear deal with Zarif at the U.N. April 27, 2015, in New York City. (Jason DeCrow-Pool/Getty Images)

What is the solution to the Saudi-Iranian conflict then? There are no obvious short-term solutions available. Rather, the first step must be to contain tensions and ensure that they don't spill over into other areas.

Second, there must be a recognition that the Middle East suffers from a diplomacy deficit. The limited diplomacy that exists must be strengthened. The recent Saudi-Iranian escalation cannot be permitted to collapse the existing diplomatic activity -- particularly not the Syrian negotiations.

While expectations on what the Syria talks can achieve must be tempered, the fact that all key outside players are at the table is an important achievement in and of itself. Neither the execution of a Shia cleric nor the sacking of an embassy -- however unacceptable -- can be permitted to scuttle the fragile Syria talks.

Part of Iran's problem in dealing with Saudi Arabia is Riyadh's inherent sense of insecurity, rooted in its outsourcing of its security to Washington.

Third, the rhetoric must cool down on both sides and the Rouhani government must ensure that the vigilantes torching the Saudi embassy are brought to trial and punished. Iran has a shameful history of failing to protect foreign embassies, and any failure to bring the perpetrators to justice will be perceived as a lack of sincerity in reducing tensions with Saudi Arabia.

Fourth, the permanent members of the U.N. Security Council must pressure both sides to deescalate and, if possible, explore opportunities to mediate the conflict. Chinese President Xi Jinping is scheduled to visit Iran and Saudi Arabia later this month. Mindful of the strong relations China enjoys with both of these Persian Gulf powerhouses and mindful of China's own interest in stability in the region, Beijing may be able to play a helpful role in defusing tensions.

In the long run, however, sustainable security can only be ensured if a new inclusive security architecture is established for the region. Any power that is excluded will develop an interest in undermining the region's security precisely because its interests are not respected. This is why the U.S.-led order for the region established in the 1990s was bound to collapse. It was based on the exclusion of two of the region's most powerful states -- Iran and Iraq -- and could only be sustained as long as the U.S. was willing to pay for it through its own blood and treasure.

It looks to the Saudis like America has simply abandoned its ally.

But until now, Saudi Arabia has sought to prevent Iran from being rehabilitated in the region's security structure. It opposed Iran's inclusion in the Syria talks, for instance, and only reluctantly agreed to partake after pressure from President Obama. Friends of Saudi Arabia need to intervene once more and convince Riyadh of the inevitable: Iran is part of the region; it is a major power and long-term stability necessitates its inclusion in any security order. The influence and privilege Saudi Arabia enjoyed under American order will no longer be the same -- because that order is no more.

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