Negotiations go nowhere. War always returns. The U.S. and Iran are arch-enemies.

For many in the Middle East, these are indisputable axioms as sure as the sun rising. No surprise then that in some quarters news of the nuclear deal between leading Western powers and Iran was as welcome as an earthquake.

For some, any détente involving Tehran and Washington threatens to upend the modicum of order in a region that doesn't normally cope well with change.

Under that order Iran played its role best as the birthplace of the "death to America" chant. For those accustomed to that thinking, dialogue between the U.S. and Iran seems unnatural — and unwelcome — after 34 years of dependable acrimony.

Naturally, the most obvious concern about this deal — certainly for Israel, as well as the Gulf Arab countries — is the nuclear threat that Iran represents for them.

Their continuing narrative, until Tehran proves otherwise, is that its regime cannot be trusted to curb its nuclear ambitions and that, deal or no deal, Iran wants nothing more than to develop an arsenal that would make it the region's indisputable strongman.

In such circumstances, these skeptics argue, dialogue isn't a firm enough approach.

Underlying their cool reaction, however, are more intriguing regional concerns about power and influence — and about the kind of change that threatens a geopolitical order that has lasted a third of a century.

Saudis upset

The weekend deal has unsettled long-time U.S. ally Saudi Arabia in particular.

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The Israeli prime minister, Benjamin Netanyahu, has called the Iran deal a historic mistake. He and the Saudis have been the main skeptics, urging the West not to trust Tehran. (Seth Wenig / Associated Press)

That wasn't immediately obvious in the terse, official statement it released Tuesday, saying the interim arrangement agreed to on Sunday could be a "preliminary step towards a comprehensive solution to the Iranian nuclear program."

Saudi officials, though, have made it clear the kingdom isn't pleased, equally by the deal as by how it was achieved — in secret, back-channel talks for months between the U.S. and Iran, hosted by Oman and never revealed even to Washington's closest allies.

There's a clear sense among the Saudi leadership that it has been slighted. That its opinion matters less and less to the U.S., and that its Shia Muslim rival, Iran, has gained — and will continue to gain — undue influence at its expense.

The real Saudi concern is that in the long term the U.S. may have much more to gain from a good relationship with Iran than a bad one — comfortable and familiar as that was.

And they're probably right.

Side benefits

For that to happen, however, the nuclear issue has to truly be put to rest.

As U.S. Secretary of State John Kerry said shortly after the interim deal was sealed, Iran must prove what it says: that it only wants a peaceful nuclear program.

The deal must be implemented, trust must be built.

That won't be easy. But the dividends for the U.S. and the West could be enormous.

To understand how, it helps to see the Middle East the way Shia Muslim Iran and Sunni Muslim Saudi see it — as a battleground, constantly caught in a power struggle between two powers vying for regional supremacy.

Generally, U.S. policy has tended to align with the Saudi position.

Tilting that slightly, to find common ground with Iran on nuclear restraint, could open a route for the U.S. to address some of the region's other most pressing problems.

For example, Iran has sway with the Syrian regime. It is also deeply wrapped up in the fate and role of the Lebanese Shia militia Hezbollah, and therefore Lebanon itself and the group's archrival, Israel.

Perhaps one day (and this clearly won't happen overnight) those are issues on which the U.S. and Iran could come to some kind of understanding.

It is why Sunday's breakthrough could eventually bring seismic change to the region.

Self-preservation

As for this deal, Iran's leadership could be the biggest beneficiary.

Its ruling clerics have clearly chosen to believe that a rapprochement with the West (and a solution to the nuclear issue, even an interim one) is a wise choice. Because it's ultimately an investment in self-preservation.

The changes they've allowed — the election of relative moderate Hassan Rouhani as president, the beginnings of an open relationship with the West and a deal that has led to the easing of sanctions — have taken pressure off the Iranian regime, both from inside and out. Pressure that must have felt threatening to the regime's existence.

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It wasn't that long ago that Iran was touting its nuclear program, with photos like this of then president Mahmoud Ahmadinejad visiting its enrichment facilities. (handout/Reuters)

Internally, the change has generated hope for a (very young) populace that has had enough of its international isolation.

And it undoubtedly helps stave off the kind of unrest Iran witnessed following the re-election of the anti-West Mahmoud Ahmadinejad in 2009, the kind of turmoil that unseated other long-standing regimes in nearby Arab countries.

In other words, the deal helps preserve the Iranian regime. It's why Hezbollah and the Syrian government applauded it. It gives Iran (and them) some breathing room.

But the deal does come with a price for Iran.

Today, and in the coming months, it costs its progress on its nuclear program. In the future, it may cost much more — maybe even co-operation with the U.S. on regional crises.

Whether Tehran will be willing to pay that price for self-preservation remains to be seen.

Still, that any of this was even a possibility after 34 years of confrontation is a huge shift indeed for the Middle East.

And if it works, the region changes in another important way.

It will have witnessed a rarity: a seemingly intractable problem solved through diplomacy and negotiation, even between arch-enemies.

Hard to believe in a region that detests change. That there was an opportunity for it to happen at all is the historic part.