If President Barack Obama does indeed attack Syria, with or without congressional approval, he will forfeit an opportunity to make headway with Iran over its nuclear programme and risk allowing Tehran once again to reap the greatest benefit from Washington's military excesses in the Middle East.
The more reasonable minds among Iranian political elites, including former President Hashemi Rafsanjani and his protege, President Hassan Rouhani, have publicly condemned Syria's alleged use of chemical weapons. In doing so, they have become targets of Iranian hardliners, who voice unconditional support for Bashar al-Assad and his regime. Even though Rouhani's rare, pragmatic messages from Tehran have caught the attention of the US, they should not be interpreted to mean that Iran would sit on the fence, if a strike is launched at Damascus.
If an attack occurs, Rouhani and company either will be pushed to the sidelines or be forced to join the chorus led by the Islamic Revolutionary Guards Corps (IRGC). As Major General Qasem Soleimani, the brilliant tactician inside the IRGC, said this week: "Some ask why we help Syria ... why we need to. Syria is part of our axis of resistance, and we are responsible for the defence of all Muslims." These words are all too familiar to Western ears, but they indicate that in Iran, where the IRGC wields enormous economic and political power, the Guards will likely have more to say than the politicians on how to react to an attack on Syria.
Thus, an attack will empower Iran's hardliners at a rare time when the US could engage more moderate leaders on a host of issues from Syria to Iran's problematic nuclear programme. And it might marginalise Rouhani and the technocrats in his new cabinet, who are aptly being called part of a "modern right" faction, for the foreseeable future. As Rouhani has stated on several occasions, his priority is lifting the severe sanctions that have been imposed on Iran by the US, the European Union and the United Nations. In other words, Iran might just be ready to negotiate on the nuclear programme.
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As the idea of an attack is debated inside the US Congress, at the United Nations, and across Europe, it is becoming clearer that the only outcome of a limited attack would be to "punish", not damage, Assad. The strategy, as outlined by Obama, would not tip the balance in the war - nor would it even eliminate Assad's stockpiles of chemical weapons.
If the attack is limited, as Obama has promised, Iran's options would include: At first, conduct an anti-American/anti-imperialist propaganda campaign in the Middle East. Washington will have created the perfect script. Syrian civilians will undoubtedly be killed, allowing the Iranians to argue that the US is hypocritical: Washington would have attacked Syria on "moral grounds", in the words of Secretary of State John Kerry, but in the process killed innocent people. An attack would surely move those sitting on the fence to sympathise with Assad and broader Shia communities in the Middle East, who would be given more evidence - at least in their minds - that the US is trying to guarantee the defeat of the Shia in order to establish Sunni-led governments in the region.
As part of this public relations campaign, Iran could aid those harmed in a potential American attack. Rouhani said last week: "An American attack will create more problems. We have done the most we can in the last few days to prevent an attack." According to some Iranian officials, evidence was provided to the Americans to show that the chemicals came from the rebels, not Assad. "However, if there is an attack on Syria, Iran will provide medicine and food to Syrians," Rouhani said.
Supreme Leader Ali Khamenei, who is largely responsible for Iran's Syria policy, would likely side with the IRGC, not the moderates, and others are already accusing the US of duplicity. "The current situation [a potential US military intervention] in Syria started with the excuse of chemical weapons," Khamenei said last week. "The Americans manipulated words to make it seem as if they have humanitarian objectives. Americans talk about humanitarian issues, but they opened Guantanamo Bay and Abu Ghraib, they were silent when Saddam used chemical weapons … on Iranians."
On September 6, Ahmad Khatami, a conservative Friday prayer leader, made a convincing argument that the US, having supported an opposition movement that has led to the killing of tens of thousands of Syrians, is now planning to attack because it lost the war through other means. "Why is America pursuing humanitarian objectives now after 30 months?" he asked. "They have supported the opposition to overthrow Bashar Assad all along, but failed."
These are powerful words that will have great meaning across the Middle East, further inflaming Arab and Iranian sentiment toward Washington. If a unilateral US attack is more extensive, and destroys Syria's infrastructure, such as its chemical stockpiles and communications facilities, this could give the green light to Iran's hardliners to launch their own targeted attacks - not on Israeli territory, but in more clever ways.
For Iran's political elites, serious damage from a unilateral attack cannot go unanswered. For example, according to the Wall Street Journal, US officials are concerned that Iranian operatives or their sympathisers will retaliate by bombing the US embassy in Baghdad.
The US has much to lose, and Iran has much to gain, if Obama authorises a unilateral attack - even if the attack has international backing. Not only will Iran appear to be justified in whatever action it takes, but US aggression will also empower the hardliners across the Middle East and in Iran by providing a credible ideological, anti-colonialist argument for increasing violence.
Just as importantly, the indirect "testing of the waters" that has been going on between Washington and Tehran since Rouhani became president a month ago would be quickly aborted. A symbolic strike on Assad - one that would do nothing to change the dynamics of the war - seems far too risky, given the likely consequences for the US.
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.