The warning came as the military moved a rocket defense system to a main northern city, and Israel's premier warned of dangers from both Syria and Iran.
Israel has long expressed concerns that Syrian President Bashar Assad, clinging to power during a 22-month civil war, could lose control over his chemical weapons. Vice Prime Minister Silvan Shalom said Sunday that Israel's top security officials held a special meeting last week to discuss Syria's chemical weapons arsenal. The fact of the meeting, held the morning after a national election, had not been made public before.
Shalom told the Army Radio station that the transfer of weapons to violent groups, particularly the Iranian-backed Lebanese Hezbollah, would be a game changer.
"It would be crossing a line that would demand a different approach, including even action," he said. Asked whether this might mean a pre-emptive attack, he said: "We will have to make the decisions."