Two weeks before crucial June elections, rival camps have refused to react to allegations that Hezbollah was behind the polarizing Hariri assassination in 2005.
Backers say the agreement with the United Arab Emirates is a model for other countries in the region. But critics worry about the UAE's ties with Iran.
Region sees it as a bulwark against Iran; US sees it as key to any peace deal.
Ahead of his Monday meeting with Obama, who supports a two-state solution, the Israeli prime minister wants to make Iran's nuclear ambitions the focus of regional diplomacy.
In an unexpected twist, the UN tribunal investigating the murder of former Lebanese Prime Minister Rafik Hariri has ordered the release of four senior Lebanese officials.
Older leaders among the minority aim to peacefully address discrimination but warn that younger Shiites are pushing for militancy.
The US Secretary of State dropped into Beirut Sunday to bolster US allies against Hezbollah supporters ahead of close parliamentary elections.
The recent spate of attacks have come as US troops are preparing to pull out of urban areas.