The fundamentalist group Hizbollah - a major loser in the event of a peace treaty - has warned of "special operations" in revenge for a car bombing in Beirut on Wednesday which killed at least three people.
"God willing, we will take vengeance on the Zionist gangs," vowed Haj Hussein Khalil, chairman of the group's political bureau, who blamed Israel for the attack.
One of the dead was named by Hizbollah as Fuad Mugniyeh, a "security official" in the militia and brother of Imad Mugniyeh, the prime suspect in Hizbollah's kidnappings of westerners in the Eighties. Imad Mugniyeh is wanted by the United States and is detested by the Syrian government. He has taken refuge in Tehran.
The renewed diplomatic movement between Israel and Syria was viewed by some analysts in Beirut as almost certainly linked to intensified pressure on Hizbollah, whose fighters have exacted a steady toll of Israeli casualties in occupied southern Lebanon.
Hizbollah's radio station in Ba'albek, the "Voice of the Oppressed," quoted the movement's spiritual head, Sheikh Mohammed Hussein Fadlallah, as saying "this crime was designed to create confusion on the domestic front".
Thursday's announcement by the official Syrian news agency that the ambassadors of Syria and Israel were to meet in Washington was bad news for militant groups opposed to the American-brokered peace negotiations.
It showed that President Hafez al-Assad was ready after a long pause to give public endorsement to the process in the face of sceptical Arab opinion. Diplomats believe the two sides have made more progress during informal discussions than official pronouncements suggest. A peace treaty between Israel and Syria would very likely be followed by another accord with Lebanon.
The Israeli Foreign Minister, Shimon Peres, yesterday complained that the Syrian-Israeli talks were "too slow and too low" because President Assad was dragging his feet and keeping talks at a junior level.
The two ambassadors, Itamar Rabinovich and Walid Muallem, were trying to narrow differences over how far Israeli troops would pull back on the occupied Golan Heights, and the timetable.
The presence of senior military officers marked a significant step forward in the discussions. It was the first time senior Israeli and Syrian officers had met officially since the ceasefire accord of 20 July 1949 signed on the Greek island of Rhodes. The countries have remained in a state of war since.
Israel's army radio said that the Chief of Staff, Lieutenant- General Ehud Barak, was present as was General Danny Yatom, military adviser to the Prime Minister, Yitzhak Rabin.
The names of the Syrian officers attending were not released although Brigadier- General Ghazi Kenaan, a close confidant of President Assad, is the member of the Syrian high command with most influence over policy in Lebanon.
Some 35,000 Syrian troops are in Lebanon to underwrite Syria's political role and to support the pro-Syrian government in Beirut.