PRINCETON ― The prospect of a U.S. military strike on Syria has dimmed following President Barack Obama’s embrace of an international initiative to take control of Syria’s chemical-weapons stockpile. The eleventh-hour U-turn on the push for military action has come against a backdrop of intensifying diplomatic pressure from the international community to avoid escalation of the violence in Syria. And that outcome is not possible without Iran.

In a joint press conference with his Syrian counterpart, Walid al-Moallem, Russian Foreign Minister Sergey Lavrov tabled a proposal, originally agreed with Iran, calling for Syria to “place chemical weapons storage sites under international control.” The stockpiles would then be destroyed and Syria would fully join the international Chemical Weapons Convention. The second component of the Russian-Iranian proposal calls for international efforts, under the auspices of the United Nations Security Council, to rein in Syrian rebel forces’ chemical-weapons capabilities.

Moallem immediately embraced the proposal. Hours later, U.N. Secretary-General Ban Ki-moon did as well, while Obama said that “I fervently hope that this can be resolved in a non-military way.”

This initiative would allow Obama to escape from a messy political and foreign-policy predicament. But the matter is far from settled: Obama has not ruled out a military strike. So here are 12 reasons why America should grasp the opportunity for a diplomatic resolution afforded by the Russian-Iranian plan.

First, there is evidence that the Syrian opposition has amassed chemical weapons. In December 2012, Iran officially informed the U.S. about chemical weapons, including sarin gas, being transferred to Syria. The U.S. declined to cooperate with Iran to press ahead on the case.

Second, U.S. military strikes on Syria have the potential to engulf the entire region ― and perhaps the U.S. ― in a broader war. After its experiences in Afghanistan and Iraq over the past decade, the U.S. can hardly afford a Syrian quagmire.

Third, with the regional Sunni-Shia conflict intensifying, the prospect of tens of billions of petrodollars backing terrorist extremists has already destabilized the region. U.S. military strikes against Syria would further fuel extremism and result in widespread atrocities by the rebels against Syrians of all faiths. Reports point to the execution and mutilation of Syrian-government prisoners. There is no doubt that the fate of Syria’s Christian and Jewish communities is now extremely precarious.

Fourth, America’s decision to back extremists in Syria contradicts its “war on terrorism” and will erode international support for it. The prospect of Iranian cooperation to root out al-Qaida extremists, which it provided in Afghanistan and Iraq, would be unlikely following any intervention.

Fifth, it is wrong to assume that without Syrian President Bashar al-Assad, Iran would lose its influence in the Muslim world as well as its link to Hezbollah in Lebanon. America’s regional position weakened, and Iran’s strengthened, following the U.S.-led invasions of Afghanistan and Iraq; U.S. intervention in Syria could reproduce that pattern.

Sixth, a U.S. attack on Syria would leave the U.S. isolated internationally and end any hope of a diplomatic resolution. There is no domestic or international appetite for another U.S. military adventure ― NATO, the G20, the Europeans, Russia, China, and 60 percent of Americans oppose a unilateral U.S. military strike.

Seventh, the civilian casualties arising from a military strike would be high. If the main justification for an attack is humanitarian ― to end the senseless slaughter of Syrian civilians ― U.S. military intervention would do more harm than good.

Eighth, U.S. involvement in Syria will breathe new life into efforts to press for a wider war between the U.S. and Iran. Al-Qaida affiliates will target U.S. regional interests in the hope that the blame falls on Iran and its militant proxies ― providing a pretext for U.S. military confrontation.

Ninth, a U.S. military strike against a third Muslim-majority country would demolish the credibility of Obama’s efforts to repair America’s image in the Islamic world. Indeed, it would most likely prove to be a strategic boon to the “resistance axis” ― Iran and Hezbollah.

Tenth, any U.S. unilateral military strike against Syria would ratchet up tensions between the U.S. and Russia. This, in turn, would strengthen the Russia-Iran alliance.

Eleventh, Iranian Supreme Leader Ayatollah Ali Khamenei has issued permission for President Hassan Rouhani’s new administration to enter into direct talks with the U.S. No better opportunity to end decades of bilateral hostility is likely to come along. In these circumstances, a U.S. attack on Syria would almost certainly dash any hope of a U.S.-Iran rapprochement for years to come.

Finally, with the moderate Rouhani now installed as President, a U.S. military strike could undermine a golden opportunity for America and Iran to reach a face-saving solution (for both sides) on Iran’s nuclear program.

Both Iran and the U.S. consider the use of weapons of mass destruction a grave crime. Indeed, Iran was a major victim of chemical-weapons attacks during its 1980-1988 war with Saddam Hussein’s Iraq. Iran can be a major partner to halt proliferation of WMDs in Syria, the Middle East, and beyond.

Iran maintains that the Security Council is the only body legally authorized to verify allegations concerning the use of such deadly weapons and to decide on the appropriate response. One promising avenue for U.S.-Iran cooperation on Syria could be joint support for a fact-finding mission by the Security Council to identify the perpetrators. Obama has his “red line” on the use of chemical weapons. So does Khamenei.

By Seyed Hossein Mousavian

Seyed Hossein Mousavian, a former Iranian ambassador and spokesman for Iran’s nuclear negotiators, is a research scholar at Princeton University’s Woodrow Wilson School of Public and International Affairs. His latest book is “The Iranian Nuclear Crisis: A Memoir.” ― Ed.

(Project Syndicate)