Late Monday, July 19, Syria reported an Israeli airstrike southeast of the northern Aleppo province but did not mention details of the target or damage.
Moscow intervened militarily in Syria's conflict in 2015, when Assad's forces were struggling to hold territory against rebel fighters.
Noting that Israel had stayed out of Syria's protracted civil war, in which Tehran backs Assad, Netanyahu said increasing Iranian encroachment required "a new calculus".
Syria said its ally would overcome what it called US "aggression", state media reported.
Why is it so hard to deter Assad? The answer is simple: Russian President Vladimir Putin is firmly on his side.
For all of the Kremlin's big talk and bluster, a military response is unlikely, with Moscow expected to stick to a barrage of diplomatic protests, experts say.
Turkey on Saturday welcomed Western strikes targeting Syrian President Bashar al-Assad's regime as an "appropriate response" to a suspected chemical attack that left dozens dead.
Saudi Arabia extends full support to US-led airstrikes on Syria, calls it retaliation for regime 'crimes'
A statement, carried by the official Saudi Press Agency, said the strikes were prompted by the "Syrian regime's use of chemical weapons against innocent civilians, including women and children".
Syrian President Bashar al-Assad said Western strikes on government military installations Saturday only made him more keen to fight back against his opponents.
The conflict has left more than 350,000 people dead, according to the Britain-based Syrian Observatory for Human Rights.
The strikes had been expected since harrowing footage surfaced of the aftermath of the alleged toxic gas attack in the Damascus suburb of Douma.
The United States is consulting with Britain and France about a joint military response to the attack in Douma that medics and rescuers said left at least 40 people dead on Saturday.
Donald Trump yet to make final decision on Syria; will speak to British, French leaders: White House
The White House press secretary said the Trump was to confer with Emmanuel Macron and Theresa May on the action to be taken against the Assad regime.
French President Emmanuel Macron said today that he would respond to "proof" that the regime of Syrian President Bashar al-Assad had used chemical weapons, "at a time of our choosing."
Germany expects to be consulted before any Western allies conduct an attack on Syrian President Bashar al-Assad's forces as the allies must be united on the matter, Foreign Minister Heiko Maas.