[新闻背景]STATE DEPARTMENT – Sectarian violence in Syria is spilling across the Lebanese border with new clashes Friday in Tripoli.

The fighting in Tripoli broke a fragile cease-fire between Sunni Muslim and Alawite neighborhoods. The violence mirrors battles across the border in Syria where mainly-Sunni militia are fighting forces of President Bashar al-Assad, an Alawite.  The United States fears the spillover of violence from Syria into Lebanon could further destabilize the region.

"We are obviously trying to be supportive of the Lebanese Armed Forces as they try to bring order and consulting with Lebanese colleagues on the situation," noted U.S. State Department spokeswoman Victoria Nuland. "But it is extremely concerning."

Many Sunni Lebanese still resent nearly 30 years of Syrian occupation during Lebanon's civil war.  Since Syrian troops withdrew in 2005, the Iranian-backed militant and political group Hezbollah has boosted its standing among Lebanese Shi'ites.

Cato Institute Middle East analyst Malou Innocent says that could be threatened by the spread of violence from Syria.

"I think we would see an erosion of political support, especially within the largely-Shi'ite constituency of Hezbollah if we see more violence," Innocent said."It simply gives more credence to the notion that Hezbollah can not create a great deal of stability within the state."

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.