Mahmoud Ahmadinejad is heading for a rocky ride at an emergency summit of Muslim leaders called by King Abdullah of Saudi Arabia that will focus on the civil war in Syria.
Iran's uncompromising pledge of support on Tuesday for Bashar Al Assad is likely to make debate especially heated - if not in public, then certainly in private.
Iran launched a pre-emptive diplomatic strike to head off its expected isolation at next Tuesday's summit. Tehran is hosting a hastily assembled meeting today of foreign ministers from a "dozen countries" that have a "principled and realistic position" on ending the violence in Syria.
The meeting will bring together representatives from Asia, Africa and Latin America, Iran's foreign minister, Ali Akbar Salehi, said yesterday.
Sitting alongside the Syrian president in a televised display of solidarity on Tuesday, Saeed Jalili, Iran's powerful national security adviser, cast the Syrian crisis as part of a wider struggle with the United States and its regional allies.
"What is happening in Syria is not an internal Syrian issue but a conflict between the axis of resistance and its enemies in the region and the world," Mr Jalili said.
Iran has long accused its Arabian Gulf rivals of arming "terrorist" Syrian opposition groups at the behest of the "warmongering" US to break an "axis of resistance" linking Iran, Syria and Hizbollah against the "Zionist regime" and America.
Mr Jalili, a personal representative of Iran's supreme leader, Ayatollah Ali Khamenei, said the Islamic republic would never allow this 30-year-old alliance to be smashed.
The collapse of the Assad dynasty would threaten Iran's links with Hizbollah, Tehran's Shiite ally in Lebanon, which gives the Iranians an invaluable proxy presence on Israel's northern border and enables Iran to project its reach into the Arab world.
In turn, the West and Arabian Gulf states accuse Iran of, at the very least, providing Mr Assad with advisers on security and communications.
Syrian rebels capitalised on those charges by claiming 48 Iranians they captured in Damascus on Sunday are Revolutionary Guards. Iran insists they are Shiite pilgrims but acknowledged for the first time yesterday that some were "retired" Guards members.
Tehran is seeking Turkey's help to secure their release but infuriated Ankara when Iran's chief of general staff warned Turkey on Tuesday to end its support for the Syrian opposition. Otherwise, Hassan Firouzabadi said, Turkey would next be afflicted by the Syrian conflict.
As host of next week's summit of the Organisation of the Islamic Conference in Mecca, it would have been inconceivable for Saudi Arabia not to invite Iran, a key member of the 57-nation bloc.
Equally, Iran would never boycott a gathering that gives it a cherished opportunity to stake its claim as a major regional player that cannot be ignored.
Experts differ widely over Saudi Arabia's game plan. Some believe King Abdullah would have preferred not to invite Iran.
Iran and Saudi Arabia, the Arabian Gulf's ideologically opposed leading powerhouses, are bitterly divided on Syria, Bahrain, and Tehran's nuclear programme.
"The Saudis were hoping Ahmadinejad would stay away," said Abdelbari Atwan, editor-in-chief of Al Quds Al Arabi newspaper, based in London. "He's embarrassed them by accepting immediately. Now he'll be the star of the summit."
Others believe Saudi Arabia will use the opportunity to unite Sunni Muslim ranks against Mr Assad's faltering regime and, by extension, to pressure Iran.
"Iran will be shown to be out of line with the consensus of the overwhelming body of Muslim opinion on Syria," said Gerald Butt, an expert on Arabian Gulf affairs. "It's a clever move by the Saudis. If Iran stayed away it would appear isolated, but it will also appear isolated when it does show up."
But there is also informed speculation that Saudi Arabia, fearful the Syrian crisis is spiralling out of control, is keen to de-escalate the situation and wants to explore whether Iran can be part of the solution.
"The Saudis are not holding back in any way on their efforts to counter Iran in the region, but they don't want to get into a direct or indirect military confrontation with Iran," said Trita Parsi, an Iran expert in Washington.
Despite visceral mistrust between Tehran and Riyadh, each has a strong incentive to defuse the Syrian crisis.
"The deterioration of the Syrian situation is in no one's interest and that may create the incentive for some sort of constructive discussion instead of posturing and accusations," said Farideh Farhi, an Iran expert at the University of Hawaii.
The Mecca summit presents Mr Ahmadinejad with a coveted chance to perform on the world stage. The summit is a challenge the publicity loving and combative Iranian president will relish.
At home he has been shut out of decision-making on key issues such as foreign policy and Iran's nuclear talks with world powers because of his long-running struggle with Ayatollah Khamenei.
The Iranian president's hardline rivals have made clear he should have no illusions that his invitation to Mecca was a Saudi olive branch.
A leading Iranian politician, Alaeddin Boroujerdi, said at the weekend: "After facing several defeats in Syria, Saudi Arabia is trying to use the sacred and spiritual atmosphere of Mecca to prove the public opinion of Muslim nations against Syria."
* With additional reporting by Elizabeth Dickinson