DUBAI, United Arab Emirates — I’VE never been in a big earthquake, but I know what one feels like now, having spent this past week in Saudi Arabia and the United Arab Emirates. The American-led interim negotiations in Geneva to modestly loosen some sanctions on Iran in return for some curbs on its nuclear program — in advance of talks for an end to sanctions in return for an end to any Iranian bomb-making capability — has hit the Sunni Arab world (and Israel) like a geopolitical earthquake. If and when a deal is struck, it could have a bigger impact on this region than anything since the Camp David peace treaty and Iran’s Islamic Revolution in the 1970s combined to reorder the Middle East.

Why? When Iran had its Islamic Revolution in 1979, it was, emotionally speaking, like a big brother who walked out, slamming the door behind him. Everyone in the family got used to his being gone. Somebody took his bedroom; somebody else took his bicycle; and everyone enjoyed the undiluted attention and affection of Uncle Sam — for 34 years. Now, just the thought of big brother, Iran, being reintegrated and having its own direct relationship with the United States has set all of America’s Sunni Arab allies — Saudi Arabia, the Gulf states, Egypt and Jordan — on edge, especially at a time when Iran is malignly meddling in Syria, Lebanon, Yemen and Bahrain.

The signs of that nervousness range from the attack on the Iranian Embassy in Beirut last week that killed 23 people to a recent essay in Al-Sharq al-Awsat newspaper by one of the Arab Gulf’s leading journalists, Abdul Rahman Al-Rashed, who wrote: “From a theoretical, political and military perspective, Saudi Arabia will have to protect itself from the Iranian regime’s nuclear program, either with a nuclear weapon or via agreements that will maintain the regional balance of power and protect Saudi Arabia and the Gulf states.” Yikes.

There are so many layers to this: Iran is big — 85 million people; Saudi Arabia is small — 20 million people. Saudi Arabia has the largest oil and gas reserves in the Middle East — and Iran is right behind. If sanctions are fully eased one day, will Iran take market share away from Gulf Arabs? The Arab Gulf is primarily Sunni; Iran is Shiite. The Iranians are developing indigenous nuclear technology; the Sunni Arabs have none.

The Geneva talks are exposing the different interests that America and its regional allies have vis-à-vis Iran, which the sanctions regime had been masking. All the years of sanctions allowed diverse parties with diverse interests — the U.S., Israel, Saudi Arabia, the other Gulf Arabs, Europe, Russia and China — to “pretend to be having the same discussion about Iran strategy, while disagreeing about the ultimate goal of negotiations and the role that sanctions could play in getting us there or not,” notes Daniel Brumberg, a Georgetown University professor and Middle East expert at the United States Institute of Peace.

If the United States is to maintain its relationships out here, and ensure that the Iran nuclear agreement doesn’t fuel more instability, the interim and final deals have to be good ones. Sanctions should only be finally removed if we can impose on Iran a rollback of its enriched fuels and enrichment technologies, along with sufficient intrusive inspections, to make an undetectable Iranian breakout to a nuclear bomb impossible.

But even if the Iranians agree to such a deal, it will be a hard sell to our allies. American officials believe that, ultimately, the only way to defuse an Iranian threat to the region is both to defuse its nuclear program and change the character of the regime, and that the two are related. Unlike our allies here in the Gulf, we believe that there is real politics inside Iran and differences within the leadership and between the leadership and the people. But those differences have been largely choked off — and the hard-liners given a monopoly on power — as a result of Iran’s isolation from the world. If we can get an airtight nuclear deal that also opens the way for Iran’s reintegration into the global economy, American officials hope that different interest groups — including more stakeholders in engagement with the U.S. and the West — will be empowered inside Iran and start to change the character of the regime.

It may not work, but it’s a worthy bet because the only real security for Iran’s neighbors can come from an evolutionary change in the character of that regime. So, if Iran’s nuclear capabilities are curbed, we can live with that bet on evolutionary change — especially since it would likely facilitate an end to the U.S.-Iran cold war, which has hampered our cooperating on regional issues. Our allies, by contrast, do not trust Iran at all and therefore don’t believe in evolutionary change there. They want Iran stripped of all nuclear technology until there is regime change.

We can’t close that gap. We can only manage it by being very clear about our goals: to unleash politics inside Iran as much as possible, while leashing its nuclear program as tightly as possible, while continuing to protect our Arab and Israeli allies. That’s why, in addition to Secretary of State John Kerry, we may also need a “Secretary of State Just for the Middle East.” Because restoring the U.S.-Iran relationship and bringing it in from the cold after 34 years is such a wrenching shock to the Middle East system, it will require daily consultation and hand-holding with all our Arab and Israeli friends.