The regional heavyweights may back opposing sides in Syria's battlefields but, at the start of an emergency Muslim summit in Mecca this week, Iran's president was seated by the side of Saudi Arabia's King Abdullah.
On the king's other side was the man who has often served as a bridge between Arabian Gulf countries and the Iranian regime, the Qatari Emir Sheikh Hamad bin Khalifa Al Thani.
It was a symbolic act but one to underscore the hope that the summit, called by King Abdullah, could build unity in the Islamic world, especially among Syria's friends and foes.
Photographs of the Saudi leader and the Iranian president Mahmoud Ahmadinejad together were splashed across the Kingdom's media yesterday.
"The Saudi leader was trying to build a bridge with the Iranian regime, saying it will be a disaster for all of us if we're divided on Syria," said Salman Shaikh, director of the Brookings Centre in Doha. "But I really don't see it bearing fruit and gaining Iranian support."
The two-day meeting of the Organisation of Islamic Cooperation has been outspoken in its criticism of the Syrian regime, which the group's secretary general said was leading the country down a "dark tunnel".
Saudi Arabia and Qatar are said to be arming rebel fighters, and several other regional countries at the summit called for Syria's president to step down.
"The Syrian regime has lost its legitimacy with the continuation of the policy of murder, bloodshed and massacres against its people," Tunisia's President Moncef Marzoukisaid.
The OIC, with 57 member countries, is expected to revoke Syria's membership in its final communiqué for "the obstinacy of the Syrian authorities in following the military option", according to a draft final statement.
The statement does not call for Mr Al Assad to step down but demands that the regime "immediately end all acts of violence" while defending Syria's "unity, sovereignty, independence and territorial integrity".
Iran has continued to support Syria's government and, yesterday, it was the only country to openly oppose Syria's expulsion.
On Tuesday, Leon Panetta, the US secretary of defence said that Washington had evidence that Tehran was organising a militia in Syria to fight on behalf of the regime. The Iranian involvement, he said, was "adding to the killing".
Analysts said that the Mecca summit was an attempt by Saudi Arabia to smooth the rift between the majority-Sunni OIC and Iran.
"This summit is a classic example of soft power," said Giulio Gallarotti, a professor at Wesleyan University in the US.
Riyadh is using its "cultural and religious powers" to try and reassert regional authority, he said.
The pageantry of this week's summit was built around the Kingdom's unique role as home to the most revered sites in Islam. Several leaders visited the mosques in Mecca and Medina.
Following the opening meetings in Al Safa palace, the King held a suhoor for guests. Saudi Crown Prince Salman urged guests to partake in Saudi culture, remembering that former US president George W Bush had once danced with a sword in Saudi folk style during his visit, the London-based Arabic daily Asharq Al-Awsat said.
But there were few signs of agreement on Syria. Neither the Saudi nor Iranian leader mentioned Syria directly in their speeches at the summit, perhaps to avoid public confrontation.
"Everyone fears a Sunni-Shia schism really blowing through the region because of the Syria situation," said Mr Shaikh. "But Saudi Arabia and Iran have different goals in Syria."
Back in Iran, the summit received far less coverage.
Analysts now worry that continued disagreements heighten the risk that the fighting and sectarian conflict in Syria could spread.
In a speech at the summit's opening, King Abdullah warned that the region was "living in a state of sedition and disunity" and proposed opening a centre for inter-sectarian dialogue in Riyadh.
"There is sectarian tension now everywhere, in Bahrain, Iraq, eastern Saudi, and Kuwait," said Dr Waleed Al Sudairy, a political science professor at King Abdul Aziz University in Jeddah. "It is actually threatening the stability of some societies, such as Iraq and Lebanon."
Saudi Crown Prince Salman said at the suhoor that the country would "severely punish" any influences that "hamper with the security and stability of this country".
About 40 heads of government from the Arab world, Africa and Asia took part in the summit.
* with additional reporting from Agence France-Presse