Saudi Arabia has reason to be apprehensive about President Barack Obama’s policy in the Middle East. But at its core, the kingdom’s alliance with the United States remains strong.

Previously alarmed by America’s refusal to prop up Egypt’s strongman Hosni Mubarak during the 2011 “Arab Spring” uprising and its reluctance to become involved in Syria’s civil war, Reuters reports that Saudi princes were horrified to see Washington reaching out to Hassan Rouhani, the new Iranian president, last month.

“The Saudis’ worst nightmare would be the administration striking a grand bargain with Iran,” Robert Jordan, a former American ambassador to Riyadh, told the news agency.

Rouhani, who is considered a moderate, was elected in June on a platform to end the international sanctions that have crippled his nation’s export economy. The sanctions are meant to dissuade Iran from developing a capacity to build nuclear weapons.

The United States seem to welcome the chance at rapprochement. In what was the first direct contact between an American and an Iranian leader in over thirty years, President Obama spoke with Rouhani on the phone after the latter delivered a fairly sober address to the United Nations General Assembly last month — marking a chance in tone from the blustering speeches his hardline predecessor, Mahmoud Ahmadinejad, tended to make.

According to Reuters, the Saudis are afraid that Obama will exploit the diplomatic opening and strike a deal with Iran: allow inspections of its nuclear sites, to make sure it isn’t developing bombs, in return for letting Iran continue to dominate Iraq, Lebanon and Syria.

Since the fall of Iraq’s Saddam Hussein in 2003 and Egypt’s Mubarak two years ago, the Saudis see themselves as the only Sunni power strong enough to withstand Shia Iran’s expanding influence in the Middle East. The two are locked in a struggle for regional hegemony that is informed by contrasting religious views: the Saudis as the guardians of Mecca and conservative Sunni hierarchy; the Iranians as the vanguard of an Islamic revolution.

Syria’s dictator Bashar Assad is Iran’s only Arab ally — which is why Saudi Arabia supports the largely Sunni uprising against his regime. Similarly, in Iraq, Iran sponsors the government of Shia prime minister Nouri Maliki which has sidelined Sunni politicians. The Saudis feel that in both power struggles, Obama’s America doesn’t have their backs.

They have reason to. Obama doesn’t seem prepared to do much to hasten Assad’s demise while his administration continues selling arms to Iraq’s central government even as it is sliding into Iran’s orbit.

Yet the American-Saudi relationship has survived major disagreements before — from the United States’ recognition of Israel in 1948 to the 2003 Iraq War. “None of these has resulted in any open breach or abridgement of the strategic partnership,” wrote Thomas W. Lippman, an adjunct scholar at the Middle East Institute in Washington DC, at LobeLog last month, “because the Saudis had nowhere else to go and the Americans were not about to cut them loose.” The foundations of the relationship, he argued, remain strong.

Today, the security and defense forces of the United States and Saudi Arabia are deeply entwined and neither side has any incentive to rupture the partnership. Americans are training and equipping the Saudi National Guard, the Saudi regime’s primary domestic security force, as they have since 1977, and are performing the same functions in the creation of a 35,000 member Facilities Security Force, which is being deployed to protect oil installations, desalination plants, power stations and other critical facilities. Saudi Arabia is in the midst of one of the largest military purchases in history, a $60 billion plus package of aircraft and other equipment, all of it American.

Even if America struck a deal with Iran, it is unlikely to sever ties with a country in which it has invested so much. Moreover, and more importantly, no great power is prepared to take over the United States’ role as the oil kingdom’s protector.