Some anti-government protests took place in Syria's southern province of Sweida over the past few days, demanding the downfall of the government.
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".
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.
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.
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.
At least 14 civilians including three children were killed in strikes on Sunday, bringing the total number of dead in the week to 530, among them over 130 children.
The US today accused Syrian President Bashar al-Assad of committing "war crimes" with Russian support in the strife-torn country where over 400 civilians have been killed in air strikes.
Over 200 people on Thursday protested outside the Russian consulate in Istanbul against the deadly assault on Syria's rebel-held enclave.
The new round of strikes by the regime of President Bashar al-Assad has killed more than 360 civilians and wounded 1,700 others since Sunday.