A protester stands in front of burning U.S., Israeli and Saudi flags with a placard bearing portraits of Iran’s Ayatollah Ali Khamenei, right, and the late Ayatollah Khomeini, during a protest in Tehran. This caption originally misidentified Khomeini. (Atta Kenare/AFP/Getty Images)

The Obama administration expects the Iran nuclear deal announced Tuesday to usher in an era of enhanced security in the Middle East. But some Arab nations are worried that it may do the opposite: allow Iran to fund proxy wars and extend its regional influence.

As leaders across the world heralded the deal, Saudi Arabia, Iran’s chief regional adversary, said it had always been in favor of an agreement to prevent Iran from obtaining a nuclear weapon. However, the statement released by its embassy in Washington hinted at its dissatisfaction, urging strict inspections and warning of “harsh and determined responses” if Iran uses the deal to incite turmoil.

In private, Saudis were more candid, with one diplomat describing the deal as “extremely dangerous.”

The agreement offers a gradual lifting of international sanctions in return for curbs on Iran’s nuclear program. Sunni Arab states such as Saudi Arabia are concerned that the sanctions ­relief may produce a flood of cash for Shiite Iran, emboldening it to pursue a more assertive foreign policy at a time when the region is racked by conflict.

Just how Saudi Arabia and its allies react to the perceived threat will be crucial to how the deal plays out, analysts said. There are fears that the nuclear agreement could spark a regional arms race.

“If sanctions are lifted, Iran will try even harder to redesign the region,” said the Saudi diplomat, who spoke on the condition of anonymity because of the sensitivity of the subject. “Iran is trying to change the Middle East, and this is unacceptable to Sunnis.”

Meanwhile, Iranian ally Syria expressed support for the deal, with President Bashar al-Assad describing it as a “great victory.”

In comments published by the official Syrian Arab News Agency, Assad said he was assured that Iran would continue “with greater momentum” to support “just issues” in the region.

Iran has used the Lebanon-based Shiite militant group Hezbollah to help prop up Assad during the four-year-old civil war in Syria. Saudi Arabia and other Persian Gulf nations have positioned themselves on the other side, backing Sunni rebels.

In Yemen, Iran supports Shiite Houthi rebels while Saudi Arabia has been conducting a bombing campaign in support of a Sunni coalition. Meanwhile, in Iraq, Iran has extended its influence politically and militarily as the government battles Islamic State extremists.

The Saudi diplomat said there is a sense among gulf leaders that the U.S. administration rushed to make a deal before the end of President Obama’s term.

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“The relationship between the gulf and the U.S. will stand, but it’s a very delicate situation,” the diplomat said. “Maybe we’ll look to other partners like China if America is giving everything to Iran.”

Obama called Saudi King Salman and other Middle Eastern leaders on Tuesday to provide assurances about the deal, according to the White House.

Abdulkhaleq Abdulla, a political analyst based in the United Arab Emirates, said the accord could trigger a nuclear arms race, though it sets back Iran’s ability to immediately make a nuclear bomb.

Under the agreement, Iran would retain the right to enrich its own uranium with some centrifuges left in place. That raises the possibility that other nations in the region will demand the same thing.

The Saudi diplomat said his nation will look at embarking on a nuclear energy program so it can be closer to having nuclear weapons if Iran breaks the deal and weaponizes its program. “We are talking about nuclear energy, but Iran was talking about ­nuclear energy when they started,” he said.

It remains to be seen whether the threats are anything more than rhetoric aimed at derailing the deal, which the kingdom hopes will stall in Congress.

One of the most contentious elements of the 18-day nuclear negotiations was a demand by Iran to lift a U.N. embargo on providing conventional weapons to the ­Islamic republic. The embargo will remain in place for up to five years, while an embargo on ballistic missiles will be in place for up to eight years.

Iran’s neighbors have expressed concerns that the lifting of economic sanctions will provide the Islamic republic with more money to fund armed groups in the region.

However, Richard Nephew, who was the sanctions chief for the U.S. negotiating team until earlier this year, said that although he expects the Iranians to spend a portion of the sanctions windfall on foreign proxies, most of it will go toward boosting the country’s struggling economy.

“The illusion, even the delusion, some people have that Iran will take every last cent and plow it into Assad and Houthis is not borne out by history, nor common sense,” he said. “They have demands at home.”

Some in the region see potential benefits from the deal. The opening up of Iran’s economy will help the United Arab Emirates, which has strong trade ties to the country. The UAE’s ruler, Sheik Khalifa bin Zayed al-Nahyan, released a statement Tuesday congratulating Iranian President Hassan Rouhani.He said he hopes that the agreement will “contribute to strengthening regional security and stability.”

Qatar and Oman also have moved toward improved relations with Tehran, noted Theodore Karasik, a political analyst based in Dubai.

Turkey, meanwhile, has indicated that it is likely to boost its oil imports from Iran, even though the two countries back opposing factions in regional conflicts.

Iran has indicated that the agreement will enable Tehran and Washington to work more closely together to fight the ­Islamic State, which holds territory in Iraq and Syria.In Iraq, both Tehran and Washington are assisting pro-government forces on the battlefield but do not coordinate directly.

“It’s in our interest to see a joint effort now to kick out Daesh,” said Ibrahim Bahr al-Uloum, an Iraqi Shiite politician who is close to Iran, using the Arabic name for the Islamic State. The nuclear accord, he said, “accepts the reality of the region by accepting Iran as a real player.”

Naylor reported from Beirut. Liz Sly in Beirut, Carol Morello in Vienna and Karen DeYoung in Washington contributed to this report.

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