TEHRAN // Iran has called the dispatch of Saudi and Emirati troops to Bahrain "heinous and unjustifiable" but there is little danger that Tehran will take overt reciprocal action, most analysts say. To do so would risk war with Saudi Arabia and possibly the United States.
Even so, the Saudi deployment and Iran's heated rhetorical response threaten to transform an issue of local unrest into a potentially destabilising regional dispute.
The events are stoking sectarian Sunni-Shiite tensions in the Muslim world and intensifying the cold war between Iran and Saudi Arabia.
By sending forces to Bahrain, Saudi Arabia has projected its regional power while showing Iran's vaunted reach to be wanting in the short term, said Farideh Farhi, an Iran expect at the University of Hawaii.
Iran has been unable to "do anything overt in support of its protesting co-religionists in Bahrain", Ms Farhi added.
Another Iranian analyst suggested it would take extreme circumstances in Bahrain for Tehran to take direct action.
Iran would "definitely" intervene to protect the Bahraini people if there were a massacre on the streets of Manama, Ali Mohtadi, a Middle East expert, wrote on Iran Diplomacy, a website for former Iranian diplomats.
He did not suggest what form such Iranian intervention could take.
For all its rhetorical bluster, Iran knows that under a collective security agreement, Bahrain's rulers can seek help from friendly Gulf Arab neighbours if the kingdom comes under threat. Iran has no treaty right to intervene on behalf of Bahraini protesters.
Moreover, Iran has no desire to give credibility to long-standing claims by Bahraini rulers that their domestic opponents are agents of Tehran. Those claims were repeated on Monday by Bahrain's King Hamad bin Isa Al Khalifa. In a veiled reference to Iran, the Bahraini monarch declared that his government had thwarted a long-standing "foreign plot".
Iran and the Bahraini opposition have always denied such accusations.
In cables released by WikiLeaks, US diplomats in Manama in 2008 also said the Bahraini government was unable to provide hard evidence to support its repeated claims that Shiite unrest in Bahrain is backed by Iran.
Bahrain's protest movement, moreover, has vigorously rejected sectarianism, insisting it represents the discontent of both Sunnis and Shiites.
A senior Bahraini Shiite opposition leader, Ali Salman, said on Sunday: "we don't want Iranians to come. We don't want a big problem in this small country." The solution to Bahrain's crisis has to be a domestic one, he insisted.
However, some analysts say Bahraini Shiite opposition groups - even if they have no ties to Iran now - may feel compelled to seek Iranian support if they come to power.
"Saudi Arabia would be their enemy, and thus they would seek out Iranian support if only to balance the Saudis," said Gregory Gause, a Middle East expert at the University of Vermont.
Tehran, meanwhile, will strive to capitalise on the propaganda front, both at home and abroad, analysts say.
"Tehran has good reasons to sit back and take a longer approach to Riyadh's move, now widely perceived in the region to have occurred with an American nod," Ms Farhi said.
Even if Iran decides to support the Bahraini opposition "subversively or challenge Saudi Arabia indirectly", it can still reap propaganda gains, Ms Farhi added.
"In the court of regional public opinion it is Saudi Arabia that will pay the cost of using a regional economic and security organisation as a vehicle for crushing domestic dissent and fanning sectarianism."
Iranian leaders are meanwhile reassuring themselves that action taken by their Gulf Arab rivals will boomerang, implying that Iran need not respond directly.
Ali Larijani, Iran's influential parliamentary speaker, gleefully proclaimed last week that Saudi Arabia and the UAE "are throwing stones at their [own] glass palaces as they invade Bahrain".
Predictably, Iranian leaders have claimed that Saudi Arabia's intervention was at the behest of the United States.
But many western commentators saw the Bahraini move as a pointed rebuff to the US.
Bahrain had responded to American efforts to reach a negotiated solution by instead inviting in troops from the Gulf Cooperation Council. Hillary Clinton, the US secretary of state, has described the intervention as "alarming".
Domestically, "the Iranian regime will use Saudi Arabia's involvement in Bahrain to advance its narrative that meddling foreigners are the real cause behind the region's troubles" according to Scott Lucas, a Middle East expert at Birmingham University in England.
Despite ruthlessly suppressing its own pro-democracy "Green Movement", Iranian leaders have shamelessly attempted to take the moral high ground on the Arab uprisings.
They have repeatedly urged governments across the region to allow their own peoples to protest peacefully to express their democratic aspirations.
Unable to respond directly to events in Bahrain, Iran has taken other measures to demonstrate its support for protesters there. Last week Tehran withdrew its envoy from Bahrain "in protest at the mass killing of the people of Bahrain by its government".
Bahrain, in turn, recalled its ambassador to Tehran in protest at Iran's "blatant interference" in its affairs.
Jittery as some of the Gulf's Sunni rulers are, they can take solace from the fact that few among their Shiite communities are likely to view Iran's experiment in direct clerical rule as a model of good governance, experts say.