As the situation in Syria continues to deteriorate, with the collapse of the Assad regime becoming increasingly more imminent, further direct intervention by Iran in the Syrian conflict in an effort to save the regime should not be ruled out. For Iran, the Assad regime represents the linchpin of their regional hegemonic ambitions, and as such preserving the regime is central to safeguarding Tehran’s axis of influence, which encompasses Syria, Iraq and Lebanon.Direct Iranian involvement in Syria, while a given, further aggravates the already volatile situation in the Middle East. The question is: when will the Western powers led by the US, the Arab states, Turkey and Israel take the necessary and credible steps to force Tehran to stop meddling in Syria’s internal affairs and prevent it from playing a direct role in an effort to quell the Syrian uprising? Having already sent military advisers along with members of Iran’s Revolutionary Guards disguised as pilgrims, and pledging firm support for the Syrian government, it is hard to imagine that Tehran will stay idle in the face of Assad’s imminent demise.The writer is a professor of International Relations and Middle Eastern Studies at the Center for Global Affairs at New York University, and a Senior Fellow and the Middle East Project Director at the World Policy Institute.Should Iran decide to further deepen its involvement in Syria, its decision would be based on long-term considerations rather than the prospect of achieving any immediate advantage.Indeed, from the Iranian perspective, regardless of how the crisis in Syria may unfold, Tehran is determined to maintain its influence, as the loss of Syria would represent a colossal defeat and severely weaken Iran’s hold on the “Shi’ite Crescent” that extends from the Persian Gulf to the Mediterranean.Whereas until recently Iran tried to obscure its involvement in Syria, in the past few days Iranian lawmakers called on their government to tell the Iranian public why Syria under Assad is of strategic importance. Ahmad Reza Dastgheib, Deputy Head of Iran’s Majlis Committee of National Security and Foreign Policy, said: “We should make all our efforts to prevent the Syrian government from falling.”In a further indication of Iran’s concerns over the future of the Assad regime, it has dispatched high-level officials including Saeed Jalili, the head of Iran’s Supreme National Security Council, to assure Assad that Iran will not allow its close partnership with the Syrian leadership to be shaken by the uprising or external foes.Tehran is not convinced, as of yet, that the Western powers (led by the United States) will in fact challenge Iran directly should Iran decide to play a more direct and active role to save both the Assad regime and its larger regional interests.Iran knows that the Western powers and Israel, along with Turkey and the Arab states, would like to pull Syria outside of Iran’s orbit. To persuade Iran that its continuing involvement in Syria is short-lived, the US, the Arab League (AL), the EU and Turkey must work in concert and adopt coercive measures to demonstrate to the Iranian mullahs that this is a no-win situation and that their continued involvement could be disastrous for the regime.The Arab states’ reaction must not be limited to another declaration of outrage as previously expressed by the Arab League. Countries such as Saudi Arabia and Qatar should openly expand their supply of military equipment, financial aid, medical supplies and other necessary provisions to the Syrian opposition in order to shift the conflict to the rebels’ advantage.Israel, which would certainly feel directly threatened by the Iranian presence in a neighboring country, should also send a clear warning to Iran (if it has not already done so): Israel will not hesitate to take any action deemed necessary to protect its national security interests.Iran also understands that should it end up being present on Israel’s borders, Israel would be provided with an excuse to attack Iranian nuclear facilities. Of particular concern to Israel are Syria’s chemical and biological weapons, which may fall into the hands of militant Islamist groups who may seek to attack Israel at the first opportune moment.Syria has become a battleground between the Shi’ite and Sunni communities.The involvement of Shi’ite Iran in Syria would assuredly change Turkey’s (which is predominantly Sunni) position altogether. Notwithstanding the ongoing discussion between Ankara and Tehran, Turkey should make it abundantly clear that Iran’s direct interference in Syria will not occur with impunity.Regardless of the existing strategic military alliance between Iran and Syria, this does not provide Iran with a license to intervene, particularly because Syria is not threatened by outside powers. Such Iranian interference should prompt Turkey to carve a large swath of land that connects Aleppo with Turkey in which a safe haven for Syrian refugees and an operational base for the Syrian Free Army would be established while, with the support of Western powers, a no-fly zone over the seized Syrian territory would be imposed.Russia, which has been adamantly against outside interference, will certainly continue to support Iran tacitly but can do little to prevent the countries concerned from acting against Iran should Tehran’s involvement become increasingly more transparent.Finally and most importantly, the US poses the greatest threat to Iran. For this reason, Iran is not likely to defy the American warnings, as stated by Secretary of State Hillary Clinton, that the US will not tolerate any power crossing such a red line. For Iran to take the American warning seriously, the threat must not be veiled by political ambiguities, as Iran will not be deterred from aiding Assad militarily unless the threat to them is clear and credible. To that end the US must take decisive measures, without necessarily placing military boots on Syrian territory.In this regard the US should move from debating the need for imposing a no-fly zone to implementing it with the support of Turkey and work with other countries, including Russia and the rebels, to safeguard Syria’s stockpile of chemical weapons.Moreover, the US must facilitate the supply of anti-tank and anti-aircraft weapons, and encourage top Syrian officials to defect now with the promise of a future in the new Syrian government.The US must also make it abundantly clear to the Syrian National Council and the Syrian Free Army that they must work in concert and send a warning to all Syrian minorities that they have a serious stake in Syria’s future and only if they work together will they will blunt further Iranian interference and ensure peaceful transition instead of plunging into sectarian war that will tear Syria apart.Short of taking these measures, the United States will not only risk the opportunity to remove Syria from Iran’s belly but also forsake the chance of playing a significant role in shaping the new political order in Syria.The ultimate question is whether Iran will gamble by taking such a risk.The answer, I believe, rests with Tehran’s paramount desire to preserve first and foremost its own regime, and that may well depend on whether or not Tehran takes the threats of Western and regional powers seriously. This is the time when only action matters.Otherwise, the region will be swept into horrifying conflagration in which every state will be a loser, especially the United States and its allies.