Israel worries that if Mr. Assad is pushed into a corner, he might create tensions by attacking targets in the Golan Heights or pushing Hezbollah to attack from Lebanon. Jordan’s monarchy is concerned pro-democracy protesters at home would be emboldened by advances by their counterparts in Syria.

Turkey and Iraq have in the past accused Syria of aiding antigovernment militias in their countries, fomenting deadly attacks. Turkey nearly went to war with Syria in 1998, because Ankara believed Syria was harboring leaders of the militant Kurdish Workers’ Party but has since dramatically improved ties. Turkey has expressed “deep concern” over the escalating bloodshed in Syria and called on Mr. Assad to begin democratic reforms without delay…

“What worries us right now is Syria,” said a senior Turkish official. “Our longest border is with Syria and we now have visa-free travel between the two countries. Plus, Syria has a Kurdish minority. So any big civil unrest there would be a concern for us.” Turkey also has a Kurdish minority.

Iraq is concerned the Syrian uprising could prompt Mr. Assad to revive support for Sunni insurgents who he backed after the 2003 U.S.-led Iraq invasion.