JERUSALEM  Israel and Syria announced on Wednesday that they were engaged in negotiations for a comprehensive peace treaty through Turkish mediators, a sign that Israel is hoping to halt the growing influence of Iran, Syria’s most important ally, which sponsors the anti-Israel groups Hezbollah and Hamas.

Senior Israeli officials from Prime Minister Ehud Olmert’s office and their Syrian counterparts were in Istanbul on Wednesday, where both groups had been staying separately, at undisclosed locations, since Monday. The mediators shuttled between the two. Syria and Israel have not negotiated this seriously in eight years.

Syria’s motives are clear: it wants to regain the Golan Heights, captured by Israel in the 1967 war, and to re-establish a relationship with the United States, something it figures it can do through talks with Jerusalem.

For Israel  which has watched the Palestinian group Hamas take over Gaza and gain ground in the West Bank, and the Lebanese group Hezbollah display raw power in Beirut  an effort to pull Syria away from Iran could produce enormous benefits. An announcement on Wednesday of a peace deal that gives Hezbollah the upper hand in Lebanon’s government probably added to Israel’s sense of urgency.