Saudi Arabia, whose late King Abdullah once urged the United States to "cut off the head of the snake" by attacking Iran's atomic program, has publicly welcomed a framework nuclear deal with Tehran, but in private mistrust remains deep.
King Salman told U.S. President Barack Obama by phone on Thursday that he hoped a final settlement of the nuclear dispute would "strengthen the stability and security of the region and the world".
However, many Saudis were concerned about the implications of the framework deal thatIran reached with world powers on Thursday, intended to open the way for negotiating a final settlement by mid-year.
"It's about verification. If they don't comply, the boycott will be reimposed. This is a reassuring result," said a Gulf source close to official Saudi thinking, but added that Riyadh was still worried about Tehran's role in the region.
"Iran may think that as a result of this accord it is on the road to respectability," he said.
The framework agreement reached in Lausanne curbs Iran's nuclear program for at least a decade and gradually lifts Western sanctions on the oil producer, but is contingent on reaching the final pact by June 30.
The conservative Sunni Muslim kingdom regards revolutionary, Shi'ite Iran as its most dangerous foe. For over a week it has bombed Houthi militia which are allied to Tehran in Yemen, just one of the region's troublespots where the two back opposing sides.
Riyadh has felt besieged by growing Iranian influence in Arab countries since the U.S. invasion of Iraq that toppled Sunni strongman Saddam Hussein in 2003, and regards the prospect of Tehran gaining a nuclear weapon as its ultimate nightmare.
However, it is also worried that a deal which lifts international pressure, including sanctions, on Iran, will allow the Islamic Republic more space to arm and finance proxies that Riyadh opposes in countries across the region.
Arab leaders have been alarmed by Tehran's drive to expand its influence and tighten its grip through allied forces and militias on Arab states, from Iraq to Lebanon, and Syria to Yemen.
REVOLUTIONARY IDEOLOGY
Ali Khedery, a former adviser to U.S. ambassadors in Baghdad, said he was concerned the accord in effect recognized Iran as a country on the threshold of a nuclear weapons capability.
Khedery raised the question of whether Iran wanted to become "a respectable and respected member of the international community", or continue as an exporter of revolutionary ideology as "a radical, militant Shia Islamist theocracy".
"If it's the latter, then this will be a disaster, and they will be able to consolidate their control over Arab regions where they are active," he said.
Analysts say it is not so much an eventual nuclear settlement that is panicking the Gulf state and its Sunni allies, but rather they fear a U.S.-Iran rapprochement will further empower Tehran and encourage it to pursue a more assertive policy in the region.
The foreign ministry in Sunni-ruled Bahrain, which accuses Tehran of stirring up unrest among its mostly Shi'ite domestic opponents, said it hoped to see "a qualitative change in Iranian policy toward non-interference in the internal affairs of countries in the region".
Tehran denies fomenting instability in Bahrain.
Saudi media cautiously welcomed the framework deal. "It seems that Iran's dream to acquire nuclear weapons dissipated in the Swiss city of Lausanne yesterday," wrote the daily al-Watan newspaper, owned by a branch of the ruling family, on Friday.
REASSURANCES
U.S. embassy cables released by WikiLeaks showed how many top Saudi princes, including the present Crown Prince Muqrin, believe Iran's leaders are bent on regional domination.
Riyadh believes Iranian backing for Hezbollah in Lebanon, President Bashar al-Assad in Syria, Shi'ite militias in Iraq and the Houthis in Yemen has destabilised the region, allowing jihadist Sunni groups could flourish.
"It's not that we expect the West's relationship with Iran will be particularly cosy... It's more that a lifting of sanctions will help Iran, even if oil prices are weaker, and that this could embolden its behavior," said a Saudi businessman familiar with official thinking.
Top princes have warned that Riyadh will seek the same terms for its own civilian nuclear plans that Tehran gets in its deal with world powers, and have also hinted that if Iran still manages to acquire a nuclear weapon, they will too.
Saudi concerns were raised by how the Lausanne talks were preceded by months of secret negotiations between Iran and the Obama administration in 2013, leaving Riyadh's princes blindsided.
It contributed to Saudi fears that Washington was steadily disengaging from the Middle East as its energy imports from the region decreased, and that it could no longer be counted on to back old allies and police the activities of common foes.
Obama addressed those concerns on Thursday with reassurances to Gulf Arab states that the deal would not affect Washington's opposition to Iran's behavior in the region, and a promise to invite them soon to Washington.
"He said our disagreements with Iran on its political behavior and its using proxies to destabilize the region, that's still there. And the sanctions related to these differences will remain in place," said Khaled al-Dakhil, a political science professor in Riyadh.
"If that's the case, as it looks now, then I believe the agreement will be acceptable to the Saudis," he added.
