Turkish Prime Minister Recep Tayyip Erdogan has accused Damascus of trying to drag his country into the Syrian "quagmire" after twin bomb attacks killed 46 people in a town on the border.
Israeli Prime Minister Benjamin Netanyahu is to visit Russia later this month for talks that will include concerns Russia may be preparing to hand over to Syria advanced surface-to-air missiles.
After months of sharp differences, Russia and the United States have agreed to push both sides in Syria to find an end to the bloodshed, offering to hold an international conference in search of peace.
Israeli raids early Sunday hit three military sites outside Damascus, the second such reported attack in 48 hours, prompting Syria's government to warn that the regional situation was now "more dangerous."
UN Secretary-General Ban Ki-moon appealed Sunday for restraint to avoid an escalation in Syria's civil war, expressing "grave concern" over Israeli air raids.
Syria's Greek Orthodox faithful bore a heavy cross on Friday as they marked the crucifixion of Christ, their country ravaged by two years of war and two of their bishops missing after being kidnapped by unknown gunmen.
President Barack Obama came close Friday to ruling out deploying US troops to Syria, saying he did not foresee a scenario in which that would be beneficial to the United States or Syria.
The United States said Thursday it was taking a fresh look at whether to arm Syria's rebels as the Damascus regime pressed an assault on opposition forces in the embattled city of Homs.
UN leader Ban Ki-moon discussed deadlocked efforts to end the Syria conflict with the major powers on Thursday amid mounting signs that peace envoy Lakhdar Brahimi is to quit.
President Barack Obama stepped up pressure on Russia over Syria on Monday, telling President Vladimir Putin of his concern about the reported use of chemical weapons by the Damascus regime.
Republican lawmakers stepped up calls for US action against Syria Sunday in the face of growing evidence that it used chemical weapons against its population in a bitter civil war.
US President Barack Obama issued a new warning to Syria Friday that using chemical weapons would be a "game changer" as he faced rising pressure at home and abroad to intervene in the civil war.
The United States said Thursday for the first time that Syria had likely used chemical weapons against rebel forces, but emphasized spy agencies were still not 100 percent sure of the assessment.
Growing speculation that the Syrian regime is using chemical weapons is turning up the heat on President Barack Obama, who has warned such a move would be a game changer.
Lebanese Shiite group Hezbollah's decision to fight openly alongside the Syrian regime will increase Lebanon's involvement in Syria's conflict, despite a policy of neutrality.
UN leader Ban Ki-moon appealed Monday for an end to outside arms supplies to rival sides in the Syrian war but the Arab League chief said that would not be possible.
Syrian rebels fighting President President Bashar al-Assad's troops won a fresh boost Monday when the European Union eased its oil embargo to let them exploit the resources they control.