Prime Minister Malcolm Turnbull has warned Russia to ensure the latest chemical weapons attack in Syria is investigated.
Russia has vetoed the United Nations Security Council investigating the attack in Douma, where up to 80 people were killed and hundreds more injured.
"We call on Russia to use its enormous influence in Syria to ensure that this is investigated and those who have been responsible are brought to justice," Mr Turnbull told Triple M radio on Thursday.
"This use of chemical warfare - whether it's in Syria or on a park bench in Salisbury in England - is a shocking violation of international law and an affront to humanity."
US President Donald Trump earlier tweeted that America's relationship with Russia "is worse now than it's ever been" - including during the Cold War.
Asked about that assessment, Mr Turnbull said it was a "very strong judgment".
"I think what he's doing there is calling on his counterpart in Russia, President Putin, to stop this disruption of the international order and bring to an end these offences against international law and humanity," he said.
Mr Trump also told Russia there would be imminent military action, as Moscow warned any US missiles fired at Syria over the deadly assault on a rebel enclave would be shot down.
"Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and 'smart!'," the president tweeted.
"You shouldn't be partners with a Gas Killing Animal who kills his people and enjoys it!", he wrote, referring to Russia's alliance with Syrian president Bashar al-Assad.
White House press secretary Sarah Sanders later clarified "final decisions" had not been made.
"We're maintaining that we have a number of options, and all of those options are still on the table," she said.
Defence Minister Marise Payne said Australia had not been asked by the US to join military action, but would consider any "reasonable request".
"It is absolutely vital the international community stands up and opposes the use of chemical weapons in the strongest possible terms," Senator Payne told ABC radio.
She pointed to Australia's support for last year's response to a chemical weapons attack, which involved about 60 missiles being fired at a Syrian airfield.
"They were targeted, they were measured and they were considered," Senator Payne said.
"If that is decision the United States takes, we will engage with them in due course."
Mr Turnbull is expected to discuss the security situation with German Chancellor Angela Merkel and British PM Theresa May during a visit to Europe next week.
Labor leader Bill Shorten said he would support action if it was similar to the "proportionate response" used by the Americans last year.
"We can't allow the use of chemical weapons against civilians to go unchallenged," Mr Shorten said.