Israel is even prepared to use military force to prevent Hezbollah, a key all of both Syria and Iran, getting its hands on Syria's advanced weaponry, Maj. Gen. Yair Golan, head of the Israel's Northern Command that borders Lebanon and Syria, warned May 31.
Hezbollah, which fought a 34-day war with Israel in 2006, reportedly possesses 60,000 missiles and rockets provided by Iran and Syria to threaten Israel.
Golan says that Syria, wracked by a pro-democracy revolution since March 15, 2011, is a "failed state."
"Terrorism is already flourishing in Syria and the terror threat toward Israel is forming," he told a Tel Aviv security conference to mark the June 7, 1982, anniversary of Israel's invasion of Lebanon.
Israel engaged in its last major combat with Syria in the first week of that conflict.
Israeli F-15 and F-16 fighters shot down 88 Soviet-built Syrian fighters, 30 percent of Syria's air force, and destroyed 19 surface-to-air missile batteries, sustaining the loss of five aircraft.
Terrorism from Syria "will not happen tomorrow but we need to be prepared," Golan warned.
"It's not hard to think of a reality in which al-Qaida elements already in Syria and fighting the regime will start to act against us.
"It's also clear possible that without a clear regime, Syria will become another area of operations for Hezbollah," he said.
Israel's concern has heightened following indications the Syrian Free Army, a rebel force comprises largely of defectors from Syria's military, has been mounting serious operations against the regime in the last few weeks.
One report this week claimed that rebels had captured a Syrian air defense base. That's not been confirmed but Israel fears it indicates Syrian President Bashar al-Assad could be losing control of military installations.
Syria is reputed to have provided Hezbollah with an unknown number of Soviet-era Scud D ballistic missiles capable of hitting all of Israel in 2010. These remain in Syria, to be handed over to Hezbollah only in the event of new conflict with Israel.
"Now though," The Jerusalem Post reported Wednesday, "with Syria in the midst of an uprising, there is concern that Hezbollah might try to move the missiles into Lebanon to prevent them from being captured by rebels other rogue elements."
Over the last six decades, Israel and Syria have fought three full-scale wars, plus the one-sided 1982 clashes, and remain in a state of war. However, their border in the Golan Heights, half of which Israel captured in 1967, has been the quietest of all Israel's frontiers since 1973.
Israel's problem, analyst Jonathan Spyer said, is that it's "entirely powerless to affect the outcome in Syria."
When the Syrian uprising began 15 months ago, Israel was concerned that the fall of the Assad dynasty, with which it has developed a modus vivendi since their 1973 war, would be succeeded by a Sunni regime headed by the Muslim Brotherhood that would be more aggressive toward the Jewish state.
Syria is widely believed to possess a major stockpile of chemical and possibly biological arms, including warheads for the Scud Ds. Israel's worst nightmare has long been Syria's use of these weapons of mass destruction.
Israel says Syria possesses Sarin, VX and other nerve gases, along with mustard gas, which can be used in missiles.
Syria is one of the few states that have never signed the Chemical Weapons Convention, and Maj. Gen. Yair Naveh, Israel's deputy chief of staff, says it "has built up the biggest chemical weapons arsenal in the world."
These are believed to be stored in 50 facilities across the country and U.S. officials say that upward of 75,000 troops would be needed if foreign forces have to secure these sights.
"There is deep skepticism and cynicism inside Israel that Israel' strategic situation would improve were the Syrian opposition to assume power -- especially since there is concern about al-Qaida and Muslim Brotherhood elements inside the opposition," Post columnist Herb Keinon wrote Tuesday.
"Prolonged instability only invites chaos, and that contains the kernels of disaster."