Cautiously, over the months, such reality checks have emerged from Iran as rebel strength and support has grown.
During the summer, several current and former Iranian diplomats published opinion articles questioning whether Tehran should stick by Mr. Assad’s regime or begin to weigh alternatives.
But Iran’s top envoy, Foreign Minister Ali Akbar Salehi, appears to reflect the seesaw views from the country’s leadership.
Mr. Salehi has urged a negotiated resolution in Syria, possibly with a deal for Mr. Assad to bow out with elections in 2014. On Saturday, however, he struck a hard-line tone by saying Tehran “won’t allow” Mr. Assad to fall — without saying what measures Iran is prepared to take.
A similar two-sided declaration was echoed by Hezbollah leader Sheik Hassan Nasrallah.
On Sunday, he urged the Syrian opposition to hold talks rather than fight, but said that predictions of Mr. Assad’s imminent ouster were mere “wishful thinking” by his opponents in the West, Turkey and Arab world.
“Iran is caught between two political paths,” said Salman Shaikh, director of The Brookings Doha Center in Qatar. “It can’t simply cut Assad loose, but it can’t hang onto him at all costs. It would be foolish to think that Iran is not actively drawing up its post-Assad strategies.”