"The Obama administration has very limited options," said analyst Mohamad Bazzi, of the Washington-based Council on Foreign Relations. "Arab and Iranian leaders are going to be more influential than the US administration in helping the factions in Lebanon reach a compromise."
Lebanese Premier Saad Hariri was in the Oval Office on Wednesday alongside President Barack Obama when the Shiite group Hezbollah and its allies resigned from the cabinet, dealing a final blow to his coalition.
Hezbollah, allies with Syria and Iran, and an enemy of the United States, for months pressured Hariri, son of assassinated premier Rafiq Hariri, to reject the Special Tribunal for Lebanon that investigated the crime.
Obama responded with strong backing of Hariri and accused Hezbollah of wanting "to block the government's ability to conduct its business and advance the aspirations of all of the Lebanese people."
Friday, the US ambassador to Lebanon, Maura Connelly, called on the political rivals to exercise restraint. There's no indication that Washington can do much more.
"Over the past two years," Bazzi said, "the administration engagement has had only sporadic engagement in Lebanon. That's partly because the US has to deal with larger problems in the region. On the other hand, Syria and Iran are constantly engaged in supporting their allies in Lebanon, especially Hezbollah."
After five years without an ambassador in Damascus, Obama believes that he'll have more influence on Syria with a representative in place. Robert Ford, the new ambassador, is scheduled to leave for Damascus on Saturday.
The Lebanese crisis likely will be Ford's first concern, but he will have no direct effect on Beirut, said Bilal Saab, a University of Maryland analyst, who argued that the United States would be most useful by keeping Hezbollah and Israel at bay.
"In the event that skirmishes flare up between Hezbollah and Israel for whatever reason, the United States must intervene immediately this time to either stop the conflict or contain it," he said. "It must not be a spectator, or worse, a cheerleader, and learn from the lessons of 2006."
Obama meanwhile must maintain his support for the STL, he said, echoing a point made by several analysts.
But the idea of unconditional support for the tribunal has critics in Washington.
Graeme Bannerman of the Middle East Institute, said that by backing the tribunal, the administration has an alternative agenda, which is to weaken Hezbollah.
"It doesn't take into consideration how the Lebanese political system works," he said. "I think we are an essential part of Hariri's problem. I think we are making his life more difficult rather than easier."
In the absence of direct influence, the United States might turn to Qatar, which managed to ease tensions in 2008.
Wednesday in Doha, in the presence of US Secretary of State Hillary Clinton, Sheikh Hamad ben Jassem ben Jabr al-Thani offered a new joint initiative with Saudi Arabia.
French President Nicolas Sarkozy proposed creating a "contact group" to negotiate a solution to the crisis. The countries involved would be the United States, France, Syria, Saudi Arabia, Qatar and Turkey.
The Western-backed Hariri returned to Lebanon on Friday from week-long talks in the United States, France and Turkey, and said the collapse of his 30-member cabinet was "unprecedented in the history of Lebanese governments."