"Our red lines have not changed," the unidentified Israeli official told English-language Israeli news website Ynetnews Wednesday night.
Syrian President Bashar Assad "should understand already that he should not play around with us on this issue," the official said. "Our policy has not changed, despite what is happening in the international arena. If something looks to us like an unusual step, it will be dealt with."
Several world powers are working toward a potential diplomatic resolution to the crisis over Syria's chemical weapons in a deal presented by Russia in which Syria would relinquish its chemical arms stockpile.
President Obama said in a nationally televised address Tuesday night he would hold off on military action and pursue Russia's proposal for international monitors to take over and destroy Syria's arsenal of chemical weapons. He said he would wait even though he believed the regime used chemical weapons to kill more than 1,400 civilians in an Aug. 21 attack near Damascus.
Obama declared Aug. 20, 2012, a chemical attack in Syria would be a "red line" that, if crossed, would be met with U.S. military force.
The Israeli official told Ynetnews Jerusalem reserved the right to respond to any attempt to arm Hezbollah, Lebanon's Shiite Islamic militant group and political party.
The Jewish state attacked Syrian missile convoys reported destined Hezbollah July 27. Israeli warplanes also carried out strikes in Syria May 3 and 5 and Jan. 31.
Among the May 5 targets was a Syrian military research center U.S. officials said was the country's main chemical weapons site.
Jerusalem has not acknowledged the attacks.
Israel sees Syria as a test case for Obama's credibility in enforcing red lines, given his promise to prevent Iran from developing a nuclear weapon, an official told Ynetnews.
"We must see what happens in the end, but it is clear our stance is that a loaded gun must be placed on the table in the form of a real military threat, and this is the appropriate position to take," the official said.
"Once Assad and the Russians realized that the United States was serious, they led the diplomatic process," the official said. "This policy holds true for Iran's future as well."
Prime Minister Binyamin Netanyahu said Tuesday Israel cannot trust anyone but itself to protect its national security.
"In the fog that covers the Middle East, we must understand that we need to rely only on ourselves," he said at a memorial service near Jerusalem.
He earlier told graduating naval officers in Haifa: "These days, perhaps more than ever, the main rule that guides me in my actions as prime minister and on which I am very particular, is: If I am not for myself, who will be? If we are not for ourselves, who will be? We are for ourselves."
His quote to the naval officers was borrowed from ancient Jewish leader Hillel.