Mohammad bin Nawwaf, the Saudi ambassador to Britain, warned at the weekend that the kingdom would not "sit idly by" if Iran acquired a nuclear weapon.
According to the British Guardian, diplomats predict that the Saudis and their Gulf neighbors, especially the United Arab Emirates, may seek to obtain security guarantees from the US in the event of a final agreement with Iran. Saudi Arabia has long signaled that it would also seek to acquire nuclear weapons – most likely from Pakistan – if Iran had them, noted the newspaper.
King Abdullah is assumed to have discussed the issue in a previously unannounced summit meeting with the emirs of Qatar and Kuwait in Riyadh on Saturday as the Geneva talks were reaching their climax.
"Anything that lessens tensions in the region is welcome," said the Saudi commentator Khaled Almaeena. "We were all on tenterhooks. Advocates of attacking Iran should know that we were facing terrible problems in the Gulf. Property values in the UAE would have gone down because people expected Iranian retaliation in case of war. We are concerned about the environment and our security.
"Both Iran and the P5+1 [the powers that concluded the accord with Tehran] will have to work hard. But we hope Israel will not throw a monkey wrench into this deal."
Sunni-ruled Gulf monarchies feel let down by their US ally and want good relations with their Shiite neighbor, Iran, but also fear the Geneva nuclear deal will boost its regional ambitions, analysts say.
Saudi Arabia and the oil- and gas-rich nations of the Gulf were weighing their reactions on Sunday hours after the agreement was signed between Iran and Western powers.
"In principle, the Gulf states want good relations with Iran," Saudi analyst Jamal Khashoggi told AFP.
"But the (Geneva) agreement has reduced the Iran problem to the nuclear level only, while its regional interference is of key concern to these countries."
Khashoggi said Gulf states "fear Iran will see this accord as encouragement to act with a free hand in the region".
Tehran is a key backer of Syrian President Bashar al-Assad, of the Shiite Alawite sect, in his fight against a nearly three-year insurrection.
The Islamic republic also feeds instability in Bahrain and Yemen through the Shiite communities there.
But President Barack Obama moved quickly to reassure US allies on Sunday, saying Washington "will remain firm, as will our commitment to our friends and allies – particularly Israel and our Gulf partners, who have good reason to be skeptical about Iran's intentions."
The Gulf states and Israel do not see eye-to-eye on Iran, said Khashoggi, adding that "the main problem of the Jewish state is (its own) nuclear" capability.
For Saudi analyst Anwar Eshki, head of the Jeddah-based Middle East Center for Strategic and Legal Studies, the deal "is not negative, but it is not enough".
Under the Geneva agreement, Iran will limit its nuclear program in exchange for $7 billion (5.2 billion euros) in sanctions relief.
Over the next six months, Iran and the United States, China, Russia, France, Britain and Germany are to negotiate a more comprehensive deal.
"We are worried," said Eshki, pointing to the $7 billion. "We need to know whether these funds will be used by the Iranian regime for its own people, or to further finance crises in the region," he said, listing Gulf nations' grievances with Iran.
Tehran "stokes sectarian tensions between Sunnis and Shiites and fuels crisis-hit areas of the Arab world, in Syria, Lebanon and Yemen", in addition to its territorial dispute over Gulf islands with the United Arab Emirates.
Distrust of Iran among Gulf states is fed by the fear that their traditional protector and ally the United States has abandoned them.
Saudi Arabia, main backer of the Syrian opposition, took issue with Obama for not attacking Syria in September despite evidence the regime used chemical weapons against its own people, killing hundreds of civilians.
According to Khashoggi, officials in Gulf countries feel the Obama administration "is no longer interested in regional problems" in the Middle East.
This stand-off approach by Washington to the oil-producing region comes with the United States set to become the world's top oil producer by 2015, because of booming shale oil output.
"Countries in the region no longer have any confidence in the United States," said Emirati analyst Abdulkhaleq Abdullah.
For him, Washington "was over-zealous" in seeking to reach a speedy agreement with Iran's new president, Hassan Rouhani.
"But they (Gulf states) do retain confidence in other allies France and Germany," he said, noting that the deal is "good in that it was agreed between Iran and the international community, not Iran and the US".
Abdullah said Gulf nations "may end up being the main beneficiaries of this agreement as it should defuse tensions in the region".