The Marine barracks bombing 25 years ago ushered in a new era of large-scale Al Qaeda attacks against the US and its allies.
In another nod to the West, Syria also sent an ambassador to Iraq – the first in decades.
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.
While the small community of adherents to strict Islam are being courted by Sunni and Shiite rivals, many worry they could bring Al Qaeda into the Lebanon conflict.
Fights between Sunnis and Alawites highlight challenges facing a sectarian-reconciliation deal signed this week.
Lebanese President Michel Suleiman's visited Damascus Wednesday, raising the prospect that perhaps hundreds of detainees in Syria will be released.