Interviewed on the U.S. "Fox News Sunday" television program, Netanyahu said Syrian President Bashar al-Assad's government would fall and that he was worried that a chaotic "regime collapse" might leave Syria's weapons sites unguarded.
"We certainly don't want to be exposed to chemical weapons falling into the hands of Hezbollah or some other terror groups. ... It's a great threat," he said.
"We will have to consider our action. Do I seek action? No. Do I preclude it? No," Netanyahu said when asked whether Israel would act alone or prefer the United States to take the lead.
U.S. Senator John McCain said that in addition to the Israeli concerns, there was a risk that the Syrian government might use chemical weapons against its opponents.
"These are helicopter gunships, tanks, artillery that are slaughtering people, and now there is a risk - and I'm not saying it is going to happen - a risk that in his desperation, Bashar al-Assad might use those chemical weapons," McCain, the 2008 Republican presidential nominee, said on CNN's "State of the Union with Candy Crowley."
White House Press Secretary Jay Carney told reporters traveling with President Barack Obama on Air Force One that the chemical weapons arsenal appeared still to be under the Syrian government's control. But a concerned Washington was monitoring the stockpiles and consulting with Syria's neighbors, he said.
"We believe that Syria's chemical weapons remain under Syrian government control," Carney said. "But given the escalation in violence, and the regime's increasing attacks on its own people, we remain very concerned about these weapons."
Israeli Defense Minister Ehud Barak said on Friday that Israel would consider taking military action if needed to ensure Syrian missiles or chemical weapons do not reach Hezbollah.
Hezbollah, which in the past has received military and financial support from Syria and Iran, launched thousands of mainly short-range rockets into Israel during the Jewish state's 2006 offensive in southern Lebanon.