Assessments of the deal are less optimistic in the Middle East than in the West.
Whether Iran complies with its promises or not, the deal reached by world powers over its nuclear program will alter the Middle East dramatically, observers and analysts say.
"I am afraid Iran will give up something to get something else from the big powers in terms of regional politics — and I'm worrying about giving Iran more space or a freer hand in the region," Abdullah al-Askar, chairman of Saudi Arabia's appointed Shoura Council, a quasi-parliament that advises the government on policy, told the Daily Star in Lebanon. "The government of Iran, month after month, has proven that it has an ugly agenda in the region, and in this regard no one in the region will sleep and assume things are going smoothly."
Western governments and the allies of Iran praised the deal as walking the world back from a possible military confrontation with the Islamic republic over its decades-long nuclear program suspected of trying to build an atomic bomb.
There was silence, however, from the capitals of Saudi Arabia, Kuwait, the United Arab Emirates, Bahrain, Qatar, Egypt and Jordan — Arab countries whose rulers belong to the Sunni Muslim sect.
Israeli Prime Minister Benjamin Netanyahu was blunt on his opinion. "What was reached in Geneva is not a historic agreement, it is a historic mistake," Netanyahu told his Cabinet on Sunday.
President Obama called Netanyahu later Sunday to underscore "that the United States will remain firm in our commitment to Israel, which has good reason to be skeptical about Iran's intentions," according to a White House statement.
Less than a day after the deal was made in Geneva on Sunday, there were differences over the two sides' understanding of the deal.
Iran President Hassan Rouhani crowed Sunday that the deal recognizes Tehran's "right" to enrich uranium; Secretary of State John Kerry said it does not. Members of Congress on Sunday — such as Robert Menendez, D-N.J. who had been pushing to strengthen economic sanction against Iran over its program — said they would hold off for now to see how things go.
FEARS OF U.S. RETREAT
Critics say the six-month deal does not freeze or force a rollback of Iran's production of nuclear fuel, as several United Nations Security Council resolutions have demanded, such as when the council called for suspension of all enrichment. Iran can continue to enrich uranium, a process that can make material for an atomic bomb.
Secretary of State John Kerry told reporters this is the first stage. The next stage "will also be even more consequential," Kerry said.
Iran agreed to put a cap on its nuclear program and give international inspectors greater access to currently inspected and new sites. Iran also agreed to stop producing medium-enriched uranium, which represents 90% of the effort required to produce weapons-grade material, and to dilute or convert that stockpile to a different form that is harder to process to fuel a bomb.
In return, the West agreed to provide Iran about $7 billion in relief on sanctions on oil and banking that were meant to get Iran to suspend production of nuclear material until international inspectors could ascertain the program has peaceful aims, as Iran claims.
The deal "looks clearly like the beginning of the end of the Iranian nuclear weapons program," said Thomas Pickering, a U.S. ambassador to the United Nations under President George H.W. Bush, and undersecretary of State under President Clinton. "What you see in this first agreement is a clear effort to make it harder for Iran to break out" and quickly produce enough uranium for a bomb.
Other Middle East analysts say that despite the U.S. role in the talks in Geneva that led to the deal, there is concern across the Middle East that the most worrying result is that it looks as if the United States is retreating from its traditional role as the guarantor of security in the region.
They say leaving Iran a threshold nuclear nation that can race across the weapons line in a matter of weeks or months means Israel and the Sunni nations must look more to each other to defend against Iran.
"Obama has now announced that the United States cannot be relied upon to stand up to Iran," says Michael Doran, who served as a Middle East adviser to President George W. Bush. "Therefore, Israel and our Arab allies will be forced to live by their wits."
Countries across the Middle East are now more likely to invest in nuclear programs of their own, form new alliances and reorient their policies to accommodate Iranian rather than American interests, Doran and other analysts say.
And Iranian aims in the region are not limited to having a nuclear program it insists is for peaceful purposes even as its ruling unelected mullahs call openly for the elimination of the "rabid-dog" Zionists of Israel.
"Iran's bottom line is that it will trade its nuclear capability with the recognition of its hegemony over the region, which is what has just happened. Saudi-Iranian tensions and (tensions in) the broader Gulf region will increase," said Nadim Shehadeh of the Royal Institute of International Affairs, a Middle East research think tank in London.
Marwan Bishara, senior political analyst at Al Jazeera, which is owned by the government of the Persian Gulf state of Qatar, said the Saudis are most alarmed by the potential U.S.-Iran detente and the rise of an unrestrained Iran on the Middle East stage.
"Further Saudi-Iranian antagonism will lead to major sectarian escalation with incalculable price for the region," he said.
Iran arms Hezbollah, a powerful militant group along Israel's northern border in southern Lebanon that has fought wars with Israel. Both Iran and Hezbollah are sending fighters to Syria to save Iran ally Bashar Assad from Sunni Muslims who have risen against his dictatorship. Hezbollah has thousands of missiles from Iran, according to the United States.
Iran also has been caught sending sophisticated weaponry to Hamas, the Palestinian terrorist group that controls Gaza Strip and has fired thousands of rockets at Israel. Egypt has accused Iran of supporting the militancy of the Muslim Brotherhood within its borders. And Gulf States such as Bahrain say it is promoting uprisings among their Shiite populations.
"Iran is not a threat only to Israel; it is a threat to the whole world and especially to the Middle East," says Prof. Avraham Diskin, a political scientist at Hebrew University in Jerusalem.
"Iran is a Shiite country and very much interested in dominating the area while most of the region is dominated by Sunni regimes that are relatively open to the West," although not progressive toward human rights.
"These regimes feel threatened and, like Israel, have a very strong interest in blocking Iran's potential nuclear military capabilities," he said.
And if they can't block it, Iran's Arab neighbors in the Gulf and Egypt "may not sit and wait" to see if Iran abides by the agreement during the next six months, he said.
Jordan, Israel and the Sunni monarchies in the Persian Gulf see the deal as the world letting Iran continue its nuclear work while pursuing its ambition of becoming the region's dominant power, says Danielle Pletka, a Middle East analyst at the American Enterprise Institute.
"The Saudis, Kuwaitis, emiratis, Jordanians all are looking at the United States, which has been their security umbrella, and they have a dawning understanding like the Israelis that America no longer has their back," Pletka said.
The Saudis have said they will seek nuclear capability for themselves, and "it's not ridiculous to assume" there may be a domino effect across the region of countries seeking nuclear weapons, she said. "I think that applies for Turkey as well."
But Jon Alterman, director of the Middle East program at the Center for Strategic and International Studies, said such worries are overblown.
"The agreement reflects the Iranian desire to change their relationship with the rest of the world, and that desire makes the Middle East safer," Alterman said.
Saudi King Abdullah has invited Rouhani to Saudi Arabia for the annual hajj pilgrimage. "You can foresee an effort to bring them closer."
There are signs that the United States is pulling back from the Middle East. Obama did an about-turn on military action against Syria even though he said a strike was necessary after Syrian forces crossed Obama's "red line" by using chemical weapons. He has welcomed a major role for Russia in negotiations in the Middle East.
Obama has cooled the once-strong relationship that the United States had with Egypt, the most populous Arab state in the Middle East, over the Egyptian military's ousting of an elected Muslim Brotherhood government. Obama canceled aid and joint military exercises with Egypt, which has openly rejected U.S. demands for quick elections, despite shared interests in fighting terrorism and maintaining Egypt's peace with Israel.
However, the United States maintains strong relations with Israel and Gulf Arab states: The U.S. Navy's 5th Fleet is based in Bahrain and Saudi Arabia earlier this year inked a $60 billion deal for high-tech U.S. weaponry.
MIXED RECORD ON NUCLEAR DIPLOMACY
Aaron David Miller, a former U.S. Middle East peace negotiator and adviser to Republican and Democratic secretaries of State, says "it's way too early" to say the agreement will transform power relationships in the region.
It has brought comparisons, however, to one of the singular achievements, and failures, of U.S. nuclear diplomacy.
The administration of George W. Bush persuaded Libya to eliminate its nuclear program entirely in the aftermath of the 2003 U.S. invasion of Iraq. Libya surrendered all of its nuclear weapons equipment to international inspectors, and 500 tons worth of centrifuges for uranium enrichment and other technology was shipped to the U.S. nuclear weapons plant at Oak Ridge, Tenn., for destruction.
But in trying to end North Korea's nuclear program in 2008, Bush inked a deal similar to Obama's in Iran that depended on the North Koreans to allow greater inspections, suspend some uranium enrichment and cease work on a plutonium plant.
Bush removed North Korea from the U.S. list of state sponsors of terrorism in return for its agreement. Just a few months later, North Korea surprised the world when it tested its second nuclear device, in violation of the pact. In February 2013, it exploded a third one.
Contributing: Michele Chabin in Jerusalem, Mona Alami in Beirut and Jabeen Bhatti in Berlin