Russian President Vladimir Putin has told Iranian Presiden Hassan Rouhani that further attacks by Western allies in Syria would inevitably lead to chaos in international relations.
In a phone conversation on Sunday, the two leaders agreed that "this illegal action seriously damages the prospects for a political settlement in Syria," Russian news agency RIA quoted the Kremlin press service as saying.
"Putin stressed that if such actions, committed in violation of the UN Charter, continue, it will inevitably lead to chaos in international relations," RIA added.
On Saturday, US, French and British forces targeted three sites in Syria, which, according to US President Donald Trump, are associated with the chemical weapon capabilities of Bashar al-Assad, Syria's president.
The coordinated attacks came as a response to the Syrian regime's alleged use of chemical weapons in Douma last week, killing scores of civilians.
The US has warned it "is locked and loaded" to strike Syria if any more chemical attacks occur.
Speaking to an emergency session of the UN Security Council on Saturday, Nikki Haley, US ambassador to the United Nations, said: "If the Syrian regime uses this poisonous gas again, the United States is locked and loaded."
Bashar al-Jaafari, Syria's ambassador to United Nations, said the attacks were an "attack against international law," and called on the three countries to stop supporting "terrorists" in Syria.
Meanwhile, Putin has described the attacks as an "act of aggression" and warned they could worsen the humanitarian crisis in Syria.