The Marine barracks bombing 25 years ago ushered in a new era of large-scale Al Qaeda attacks against the US and its allies.
The weekend bombing that killed at least 17 people was the worst of its kind since Syria's battle with the Muslim Brotherhood in the 1970s and 80s.
Critics say the deal, which they see as lopsided, could embolden Hezbollah.
The Lebanese Shiite group is recruiting Sunnis, training in Iran for a possible second war with Israel.
The USS Cole has deployed off the coast of Lebanon as that nation's political crisis deepens.
But many young activists are still struggling to maintain the movement that followed in the wake of Hariri's death.
Supporters of both pro-Western factions and Hezbollah militants honored their respective slain leaders.
Imad Mughnieh, suspected of planning kidnappings, hijacking, and attacks in Beirut during the 1980s and '90s, was killed in Damascus Tuesday night.