Saudi Arabia's top diplomat is expected in Damascus on Tuesday, Syria said, ending more than a decade of diplomatic deep-freeze between the two countries just weeks after a landmark Saudi-Iranian rapprochement.Recent months have seen increasing Arab engagement with Syrian President Bashar al-Assad, who has been politically isolated in the region since the start of the civil war in 2011.A flurry of diplomatic activity has been underway in the past week as regional relations shift following a decision by Saudi Arabia and Damascus ally Iran to resume ties.