The violence near the Israeli-occupied Golan has jarred Israel, which this week twice shot back after stray Syrian fire hit its side -- the old foes' first armed engagement over the strategic plateau since 1973.
Israel had warned Assad to prevent violence spilling over, but on Wednesday its defense minister, Ehud Barak, said the Syrian ruler's hold was undergoing "painful disintegration".
"Almost all of the villages at the foot of this ridge, and on upward, are already in rebel hands," Barak said during a visit to the Golan, referring to the eastern foothills that where Syria's army has been battling insurgents.
"The Syrian military is displaying ever-diminishing efficiency," Barak said.
Prime Minister Benjamin Netanyahu, who accompanied Barak to the Golan on a trip kept under wraps until they departed, said Israel was worried that its Golan troops and settlers might come under fire and that enemy forces might penetrate the plateau.
In a separate statement, Netanyahu said there were "cracks" in Assad's regime and that "forces from the global jihad, even more hostile to Israel (were) taking hold" within Syria.
"Global jihad" is Israel's term for al-Qaida and its affiliates around the world.
With the Golan relatively quiet on Tuesday after two days of shooting across the ceasefire line, Israeli television showed images of Syrian troops withdrawing and said Israel had received assurances that the Syrians would try not to fire over the line.
Israel's Foreign Ministry said on Wednesday it knew of no such message from Syria, and the United Nations observer force on the Golan declined comment.
JERUSALEM (Reuters) -- Syrian President Bashar Assad's forces are faltering against rebels, some of whom are dug in on the eastern foothills of the Golan Heights, Israel said on Wednesday.