By Eric Vandenbroeck

The Sunni-Shia struggle is starting to reach heights never before seen in the modern era.

From the Iranian point of view, the situation is perhaps worse than during the war with Iraq in the 1980s because at the time Tehran had major influence on the other side of Baathist Iraq in Syria and Lebanon, providing Iran with some respite. In the current situation, where Iran's influence in Syria (and by extension, Lebanon) is slipping, Tehran is looking at a return to the days of the Ottoman-Safavid rivalry, when the entire Persian western flank from Iraq to the Mediterranean was in hostile hands. This time it is not the Turks who the Iranians have to worry about; in fact, Ankara is also fearful of the Saudis' use of jihad against the Iranians in Syria, which is bound to produce jihadism.

For Iran, the possible impending collapse of the Bashar al Assad regime in Damascus represents a massive event and -- in the words of Ali Akbar Velayati, Supreme Leader Ayatollah Ali Khamenei's top international affairs adviser -- a red line. Those remarks, issued last week, were a message to the Saudis that the Kingdom is looking at a major regional sectarian conflict if it continues to support the dozens of jihadist militias fighting the Syrian regime. The suggestion is that it is better for both sides to seek a negotiated settlement. The Saudis responded a few days ago when their foreign minister, Prince Saud al-Faisal, on Tuesday said that a political resolution to the Syrian crisis was unlikely -- a signal that Riyadh is not interested in negotiations.

From the Saudi point of view, this is a historic opportunity to decisively roll back Iranian encroachments from the Sunni Arab world. The Arab Spring and the Saudis' own succession impasse are increasingly creating uncertainty, and the Saudis want to be able to tackle the Iranian threat so as to be in a better position to manage the Kingdom and the Arab world. Riyadh also knows that demographics in Syria work in its favor -- the country is at least 60 percent Sunni -- which it is complimenting by sending jihadists who share its view of Iran, the Shia and the Syrian regime to the country.

Nationalist and secular-leaning forces want to topple al Assad but do not want to fight the Shia and Iran. Therefore, the Saudis are once again flirting with jihadist and sectarian militias who will not only fight in Syria but will also take the battle to Iraq and help weaken the Shia-dominated political order there.

Tehran has few options. It has to fight back and, in the event that there is no deal, it has to mount a powerful insurgency to prevent its enemies from controlling Syria. It is also trying to strengthen its position by shaping regional perceptions that Riyadh is pursuing a sectarian agenda in the hope that it can capitalize on uneasiness among states like Turkey, Qatar and Egypt that do not share the Saudis' anti-Shia and anti-Iranian stance. Finally, it is working on highlighting the al Qaeda threat, hoping to get the United States and the West to abstain from an aggressive push against the regime in Damascus.

The Americans do not want al Qaeda to benefit from the crisis in Syria. As it is, they have a jihadist problem in the Maghreb, Sahel, Afghanistan, Pakistan and Yemen. There is also the rise of political Islam in the form of the Muslim Brotherhood, especially in Egypt, which is adding to the uncertainty in the region.

But Washington also has an interest in undoing the effects of regime change in Iraq and weakening Iran. Therefore, it will cautiously use the sectarian fault line running through the region to try to maintain a difficult balance of power. What this means is that a major, long-term geopolitical conflict along the northern rim of the Middle East is highly likely.