One recent cool and sunny afternoon in Lebanon's northern city of Tripoli, Sheikh Bilal Baroudi, a Sunni Salafist cleric, showed me the charred remains of the Salam mosque. He was preaching there on Aug. 24 when a bomb detonated, killing dozens of worshippers. Only a few walls remained.

While a construction crew worked tirelessly that afternoon to rebuild the gutted building, Baroudi blamed the attack on a local group of Alawites who back the Alawite president of Syria, Bashar al-Assad. He said his mosque -- as well as the Taqwa Salafist mosque in Tripoli, which was bombed that same August day -- had been targeted because members of both congregations support the insurgency in Syria.

The Alawites are a minority sect with ties to the form of Shiism prevalent in Iran. They comprise a small portion of Lebanon's population of approximately 4.4 million people. The percentages of Shiites and Sunnis are not known and are a matter of speculation because the last census conducted in Lebanon was in 1932.

The small Alawite community of Tripoli, Lebanon's second-most important city, has long been at odds with the local Sunnis. And soon after the Syrian uprising began, clashes broke out in the mountainous areas to the north of the city, between the Alawite-dominated neighborhood Jabal Mohsen and the Sunni-dominated Bab al-Tabbaneh.

"The Syrian regime wants to transport the conflict to us here," Baroudi told me that day. For him, as well as many other Sunnis I have met in this part of Lebanon, the twin bombings of the Tripoli mosques last summer were intended to heighten sectarian tensions. Baroudi told me Assad's regime was trying to foment violence by convincing local Shiite groups that the Sunnis were out to get them -- and then supplying them with explosives.

Whether or not this is true, there is no doubt that the sectarian divide in Lebanon has indeed been widening. Just this week, two explosions hit the Iranian Embassy in Beirut, in suicide attacks for which Abdullah Azzam Brigades, a Lebanese Sunni group with links to al Qaeda, has claimed responsibility.

The struggle to dislodge Assad has disturbed an unwritten social contract among Lebanon's many sects. The country secured a fragile peace after enduring a civil war from 1975 to 1990. Syria occupied Lebanon from 1976 until 2005, when it withdrew only due to international pressure. Syria has had a longstanding claim on Lebanon; during the Ottoman era, Lebanon was part of Greater Syria.

But stability has been increasingly difficult to maintain since Hezbollah, the Lebanese Shiite movement backed by Iran, has actively supported Assad financially and militarily, including fighting alongside his troops inside Syria.

The war next door is also inspiring distorted ideas. Baroudi and other Salafists accuse the United States of enabling the Shiites to stay in power in Syria. Some of the Salafists in Tripoli point to President Barack Obama's historic call to the newly-elected President Hassan Rouhani of Iran, as well as talks on Iran's nuclear program, as evidence that the U.S. government is now backing Iran in the Middle East.

According to Baroudi, Washington "can no longer fight wars directly," and needs Tehran "to take on this role." And there is no ally "more loyal or more successful or more powerful" than Iran "to force the region into submission, weaken the Sunni, and extort the Gulf."

In October, in Bab al-Tabbaneh, one Salafist sheikh -- who wished to remain unidentified out of concern for his safety -- complained that even as the U.S. government had become less critical of Hezbollah because of warming ties with Iran, it readily condemned Sunni extremists. He did not respond when I reminded him that Washington considers Hezbollah to be a terrorist organization.

Such misperceptions have a radicalizing effect. And many Lebanese academics, journalists, and officials I have spoken with over the last year believe that is precisely what Assad had hoped for: It bolsters the argument that his regime, no matter how brutal, is a better option than any Sunni-led government.

"Assad wants to make the Syrian revolution not one of people against Assad, but one of Shiite-Sunni strife," Ali Amin, a journalist at Al Balad newspaper in Beirut and an expert on sectarianism, told me.

If this is indeed Assad's strategy, it appears to be working. Western governments, as well as Russia and Iran, seem to be scrambling to maintain stability in the region by negotiating a settlement with Assad that would leave his regime intact. They are hoping to hold negotiations in Geneva in December.

Some Sunnis in Lebanon, perceiving the U.S. government to be endorsing the status quo in Syria, are feeling more threatened, and are increasingly ready to take up arms to fight for their survival. Such feelings of anger and desperation could be the motivation behind this week's attack on the Iranian Embassy and future violence inside Lebanon, which undoubtedly would end Lebanon's fragile social contract.

One consequence of this assessment -- however misguided -- is that while progress toward a deal over Iran's nuclear program would calm minds in the West, it would unnerve many Sunnis in the Middle East. Their main concern is the Shiites' increasing influence, with Iran as their protector.

As perceptions of Iran's growing power increase among the Sunnis, it is imperative for the United States to send a signal to the region that it is not taking sides in the sectarian conflict, which certainly will continue.