Dozens of companies tied to Iran's elite Revolutionary Guards, a military force commanding a powerful industrial empire with huge political influence, will win sanctions relief under a nuclear deal agreed with world powers.

The development is likely to anger critics of the accord, not least in the US and Israel, but may be welcomed by Iranians eager for Iran to reopen to the outside world. The IRGC will act for Western firms in many ways as a gatekeeper to some of the most lucrative areas of Iran's economy.

Such is the clout of companies with ties to the Islamic Revolutionary Guards Corps (IRGC), which sees itself as the defender of Iran's Islamic revolutionary ideals and bulwark against US influence, that their release from financial curbs could of itself help ease return of swathes of the economy to the mainstream of world trade.

The process is complex and will unfold in stages, with some firms obliged to wait eight years for sanctions relief and others who can expect no concession even then from Washington, a reflection of concerns over activities beyond Iran's borders.

Among the latter is the IRGC's construction arm Khatam Al Anbia, controlling at least 812 affiliated companies worth billions of dollars and deemed by Washington "proliferators of weapons of mass destruction".

The European Union will delist the company for sanctions in eight years, while the US will maintain its measures against the firm. Foreign businessmen must gauge at that time to what extent they can trade with such partners without themselves inviting US measures.

In all, about 90 current and former IRGC officials, entities such as the IRGC itself, and firms that conducted transactions for the Guards will be taken off nuclear sanctions lists by either the US, EU or United Nations, according to a Reuters tally based on annexes to the text of the nuclear deal.

A handful will see EU sanctions removed once the nuclear deal is enacted on "Implementation Day" expected within the next year. Others such as Bank Saderat Iran (BSI), accused by Washington of transferring money to groups it deems "terrorist", such as Hezbollah and Hamas, will have EU sanctions lifted in eight years; but US measures will remain in place.

Any IRGC companies delisted at the implementation stage would be able to "move money through global banks, access the SWIFT financial system, obtain and extend credit", among other activities, said Mark Dubowitz, executive director of the Foundation for Defense of Democracies. They could also get the backing of European export financing.

Most IRGC entities such as the elite Quds force, which carries out overseas operations, and Guards' airforce and missile command will not be de-listed by the EU until the second phase in some eight years. But all will remain then under US sanction for "terrorism support activities" or as "proliferators of weapons of mass destruction".

These groups include names likely to cause controversy, at least in the West.

Among them, Quds commander Qasem Soleimani. He has had a high-profile role in advising Shi'ite militia leaders in Iraq as well as the forces of President Bashar Al-Assad in Syria.

Also on the list for EU sanctions relief in around eight years is Ahmad Vahidi, a former head of the Guards wanted by Interpol for his alleged role in the 1994 bombing of a Jewish community centre in Buenos Aires. Vahidi denies involvement.

Of those who will see nuclear sanctions eventually removed, the EU will delist Soleimani for nuclear sanctions but maintain measures for issues related to Syria and terrorism.

Iran denies any involvement in terrorism.

The benefits that will accrue to the Guards, its recent annual turnover from all business activities estimated at around $10-12 billion by one Western diplomat, have been the focus of much of the outrage in US Congress over the deal.

Western critics say the deal does not in any case go far enough to ensure Iran will never be able to develop a nuclear weapon - an ambition Iran denies. Republicans in Congress, and some Democrats, are pursuing a motion to scrap the deal.

BUSINESS INTERESTS

Dozens of smaller companies linked to the Guards, some of which are directly involved in the purchase or manufacture of military materiel, are also scheduled for sanctions relief.

Among those is the Iran Aircraft Manufacturing Company, which builds military aircraft and unmanned aerial vehicles, and Marine Industries, responsible for marine military acquisitions for both the IRGC and Iran's navy, according to the US Treasury. The EU will lift sanctions in about eight years while the US will retain them.

Under sanctions, the Guards were still able to thrive by controlling the smuggling of banned goods across the Gulf and from neighboring countries, experts say.

So widespread are IRGC business interests that providing significant sanctions relief in Iran may be hard without relaxing restrictions on some key companies to some degree.

"Without delisting certain parties on implementation day --some of the banks or oil-related companies, for example --sanctions relief would have been hard," said Zachary Goldman, a former adviser at the US Treasury and now at New York University's Center on Law and Security.

Now, the Guards will be able to lever their dominance in Iran's economy to serve as a conduit for the new business flowing into Iran, and will likely demand joint ventures, shared profits, and other benefits from companies seeking to access Iran's lucrative markets, Dubowitz said.

"Any company that wants to do business in a key strategic sector of Iran's economy will have to do business with the Revolutionary Guards," he said.

The Obama administration has sought to play down benefits potentially accruing to the Guards from the deal, which eases sanctions in return for curbs on Iran's nuclear programme.

James Clapper, the US director of national intelligence, said Iran would likely spend most of its sanctions relief on domestic priorities and that groups like the Guards never lost funding even during the worst of the country's economic crisis.

"They've been funded anyway even with the sanctions regime," Clapper said at an Aspen Institute security forum in July. "So I'm sure they'll get some money but I don't think it'll be a huge windfall for them."

Foreign firms will have to act with caution in opening ties with Iranian companies even as EU sanctions unravel. EU and US policies diverge at points, leaving some room for uncertainty.

In testimony to Congress in July and August, senior Treasury officials said their department would continue to enforce sanctions targeting the Guards.

"A foreign bank that conducts or facilitates a significant financial transaction with Iran's Mahan Air, the IRGC-controlled construction firm Khatam al-Anbiya, or Bank Saderat will risk losing its access to the US financial system, and this is not affected by the nuclear deal," said Adam Szubin, the Treasury's acting under secretary for terrorism and financial intelligence, in written testimony to the Senate Banking Committee in August.

The Iranian Mahan Air airline is accused by Washington of shipping arms for the IRGC and providing transport for the Lebanese Hezbollah militia which it considers a terrorist group.

Szubin acknowledged that some companies sanctioned in the past for dealings with the IRGC will see sanctions relief.

"There are companies who have done arms' length transactions with the IRGC over time that we've designated for conducting business for the IRGC, we have companies like that that are due to receive relief at various phases under the deal."

But the Obama administration's statements have done little to alleviate the concerns of members of Congress who argue that the Guards will benefit greatly from the lifting of sanctions.

"They're going to be the number one beneficiary of the sanctions lifting," said Bob Corker, chair of the Senate Foreign Relations Committee, at a hearing about the deal last month.  - Reuters