To critics, lifting sanctions on Iran under an historic deal reached Tuesday will help its ability to foment unrest in the Middle East, but some experts say the nuclear issue has become a sideshow to more immediate crises in the region.
After years of negotiations, climaxing in an 18-day marathon in Vienna, world powers secured a deal with Tehran aimed at ensuring Iran does not obtain the nuclear bomb.
Just a few years ago, Iran's nuclear programme and fears of an arms race with its rivals in the Gulf were paramount issues.
Many saw a deal as coaxing Tehran back into the diplomatic fold and easing tensions in the region.
But since then, the Middle East has erupted with a string of wars and insurgencies that have muddled the situation on the ground.
The West finds itself on the same side as Iran against the brutal militants of the Islamic State group in Iraq, even as they support opposing parties in the Syrian civil war next door.
"The regional environment has become a lot more complex and it's only becoming more complex," said Shashank Joshi, an analyst at the Royal United Services Institute (RUSI) in London.
"Iran and the US are both much more stretched than they were a few years ago and don't want any extra turbulence caused by the nuclear issue."
- 'Regional dominance'? -
The deal agreed Tuesday puts strict limits on Iran's nuclear activities for at least a decade.
In return Iran will get sanctions relief although the measures can "snap back" into place if there are any violations.
Many worry about what Iran will do with the windfall -- estimated at between $50 billion and $100 billion -- that will be unlocked when international sanctions are lifted.
The White House argues Iran has too many problems at home to be throwing away cash on foreign trouble-making.
But critics of the deal, particularly Israel and its supporters in Washington, say the money will embolden an aggressive Iran.
"Iran seeks regional dominance," wrote former NATO Europe Commander James Stavridis in Foreign Policy magazine last month.
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"The next problem will be an ambitious and relatively well-funded nation with distinct ambitions in not only its region, but globally."
Others dispute the portrayal of Iran as greedy for power, chomping at the bit to rebuild its ancient empire.
"The idea that Iran will put all its money into destabilising activities abroad -- that's a caricature," said Simond de Galbert, a French diplomat who worked on the Iran negotiations and is now a visiting fellow with the Center for Strategic and International Studies in Washington.
"Iran has been able to extend its influence mostly because the states in the region are weak -- the Syrian state has collapsed, the Iraqi state cannot look after its own security. The same is true in Yemen and to some extent in Lebanon," he said.
- 'Always want more' -
There are still fears a deal could trigger an arms race, as Iran's rivals in the Gulf and beyond do not believe Tehran will end its perceived desire to get the nuclear bomb.
Israeli Prime Minister Benjamin Netanyahu, swiftly reacting to the nuclear deal, called it "a historic mistake" and hinted he remained ready to order military action.
The late Saudi king, Abdullah, bluntly warned a US ambassador in 2009: "If they get nuclear weapons, we will get nuclear weapons."
The agreement with Iran could prove a boon for the Gulf monarchies, allowing them to squeeze endless quid pro quos from Western countries, said Joshi.
"You can never reassure allies enough. They will always want more, almost guilting them into it," he said.
"But we'll also see hedging behaviour from the Saudis. They have already been working more closely with Qatar and Turkey -- two countries they had previously been estranged from."
The lifting of punishing economic sanctions, though not the embargo, will also allow Iran to resume oil exports.
More Iranian oil, though, will add to a supply glut, which has already depressed prices. Prices fell quickly on US markets Tuesday.
While many have tried to paint the Iran deal as symbolic of a larger rapprochement with the West -- for good or ill -- those involved say the focus has never really gone beyond the narrow issue of nuclear weapons.
"The sanctions were only ever about nuclear proliferation, and the agreement to lift them should only be judged on that basis," said De Galbert.
"If there's something problematic about Iran's wider actions in the region, we have to find another way to counter that."