Innocent says violence on both sides of the border may undermine Iran's ability to resupply its Lebanese proxy, Hezbollah.

"The Assad regime does remain pivotal for Iran's continued support to Hezbollah. So if Assad goes, you really see a pillar of support for Iran plummet," Innocent explained.

Lebanese security forces have tried to separate Sunni and Alawite rivals.  Paul Salem, who directs the Carnegie Endowment's Middle East Center in Beirut,  says that while the violence is likely to continue in the north, it may not spread elsewhere in Lebanon.

"I think it will remain within these limits of escalation then calming down, escalation and then calming down, for the foreseeable future," Salem said. "But it's certainly one of the indications of the inter-connectedness between the crisis in Syria and the situation in Lebanon."

Lebanese Prime Minister Najib Mikati is working with local religious leaders and lawmakers in Tripoli to stop the fighting after 15 people died in similar sectarian violence in June.  But some Lebanese say he is not doing enough.

New Syria envoy Brahimi hints at difficult mission ahead during un appearance

The Washington Post By Associated Press, Published: August 25

UNITED NATIONS — The new U.N.-Arab League envoy to Syria hinted Friday at the immense challenges he faces trying to negotiate an end to that country’s civil war amid rapidly escalating violence, saying the mission left him “flattered, humbled and scared.”

Lakhdar Brahimi, a 78-year-old veteran Algerian diplomat and former U.N. envoy to Afghanistan and Iraq, made his comments alongside Secretary-General Ban Ki-Moon in his first public appearance at the United Nations since accepting the job abandoned by Kofi Annan earlier this month.

“Secretary-General, when you called me I told you that I was honored, flattered, humbled and scared, and I am still in that frame of mind,” Brahimi said during a photo opportunity where he did not take questions.

The Syrian people will be “our first masters,” he added. “We will consider their interests above and before everything else.”

Ban said Brahimi’s “extraordinary talent and expertise” will be needed for the crucial task of bringing peace and stability to Syria and promoting human rights there.

Brahimi had needed at least a week to deliberate before finally accepting the job last Friday.

Gerard Araud, the French U.N. ambassador and current Security Council president, has called the special envoy post something of an “impossible mission” and said he could understand why someone would take their time before deciding to take it.

Brahimi arrived here Thursday for a week of meetings with senior officials. He met with Araud and will soon hold an informal meeting with Security Council members, Araud’s spokesman said.

Brahimi, who will be based at U.N. headquarters in New York when his job starts Sept. 1, plans next to go to Cairo for meetings with the Arab League.

A frustrated Annan announced his resignation after failing to broker a cease-fire despite developing a six-point peace plan which the Syrian government initially agreed to but then failed to implement.

Activists say about 20,000 people have been killed since March 2011.

The last of the U.N. military observers left Damascus on Thursday. The unarmed observers, who had been mostly confined to their hotels since June, were part of Annan’s failed plan.