The sabre-rattling over an alleged chemical attack in Douma, outside Damascus, reached a new peak this week as US President Donald Trump warned of striking Syria with "smart" missiles and Russia vowed to shoot them out of the sky.
As the Organisation for the Prohibition of Chemical Weapons (OPCW) said its experts were travelling to Syria and would start investigations on Saturday, here is a breakdown of where each country stands on the prospect of retaliatory strikes.
On Wednesday, Trump took to Twitter directing a stark warning of retaliatory strikes at the Kremlin. He wrote: "Get ready Russia, because they (missiles) will be coming, nice and new and 'smart'!"
In the war of words, he even went as far as saying the US relationship with Russia was "worse now than it has ever been, and that includes the Cold War".
His stance appeared to soften Thursday, however, when he suggested there would not be imminent action on his part.
"Never said when an attack on Syria would take place. Could be very soon or not so soon at all! In any event, the United States, under my Administration, has done a great job of ridding the region of ISIS. Where is our 'Thank you America'?" he wrote on Twitter.
Moscow warned it would intercept any strikes in response to Trump's threats.
Senior officials, including the head of the military, said that US missiles would be shot out of the sky and their launch sites targeted if Russian personnel would come under threat.
"The immediate priority is to avert the danger of war," Moscow's UN ambassador Vassily Nebenzia said on Thursday.
Russia has demanded further investigation into the alleged chemical attack with foreign ministry spokeswoman Maria Zakharova saying claims around the attack were fake and warning the West to carefully consider the consequences of their actions.
Syrian President Bashar al-Assad spoke Thursday warning the West against attacking Syria, labelling accusations about the suspected chemical attack on Douma "fabricated."
Syrian TV quoted Assad at an Iranian delegation in Damascus as saying: "Any possible action will only cause more instability in the region and threaten international security and peace."
French President Emmanuelle Macron said he had "proof" that chlorine was used in Douma and that the Syrian government was responsible for the attack, which Syrian activists said killed over 40 people.
The French response would be put on hold, however, until all facts were known.
Britan made clear that it was ready to back its US allies in military action against Syria.
The country said it is "highly likely" chemical weapons were used and ministers agreed action was necessary to "deter the further use of chemical weapons by the Assad regime", but the shape that any military involvement by the UK would take was not specified.
Along with Macron, Chancellor Angela Merkel expressed concern about the "erosion" of a worldwide ban on chemical weapons, according to a German government statement.
Merkel said Thursday that Germany would not participate in strikes on Syria and that the "whole spectrum of measures must be considered" when responding to the situation.
"Germany will support all activities with the UN security council," she added.
Prime Minister Paolo Gentiloni said in calls with other Western leaders that Italy would not directly be involved in military retaliation.
But owing to “current international and bilateral accords," Italy would "continue to offer logistical support to allied forces,” he said in a statement.
Turkish President Recep Tayyip Erdogan condemned Assad for killing "innocent kids in the Douma chemical attack".
He also addressed all nations warning against the use of Syria as an arena to flex military muscle.