The US and Russia have traded barbs at a UN Security Council meeting on the alleged chemical attack in Syria.
Russian envoy Vassily Nebenzia said the incident in Douma was staged and that US military action in response could have “grave repercussions”.
US Ambassador Nikki Haley said Russia had the “blood of Syrian children” on its hands.
Earlier, the UN human rights chief said world powers were treating chemical weapons use with a “collective shrug”.
US President Donald Trump has said “major decisions” on Syria will be made in the next two days.
Ms Haley said that if the UN Security Council acts or not, “either way, the United States will respond”.
“Meetings are ongoing, important decisions are being weighed even as we speak,” she said.
Washington has not ruled out military strikes. In April last year, the US fired cruise missiles at a Syrian airbase after a Sarin nerve agent attack on the opposition-held town of Khan Sheikhoun killed more than 80 people.
The estimates of how many people died in Saturday’s suspected chemical attack range from 42 to more than 60 people, but medical groups say numbers could rise as rescue workers gain access to basements where hundreds of families had sought refuge.
The US, France and UK have led international condemnation of the alleged attack, with the Syrian government and its Russian backers denying any responsibility.
In an angry statement at the UN, Mr Nebenzia of Russia invited investigators from the Organisation for the Prohibition of Chemical Weapons (OPCW) to fly to Syria as soon as Tuesday, saying that Russian troops would escort them to the site of the alleged attack to prove its account of events.
Mr Nebenzia, presenting Russia’s case that rebels in Douma staged the attack for their own ends, painted the incident and its fallout as part of a US-led effort to hurt Russia with a “broad arsenal of methods”, including slander, insults and “hawkish rhetoric”.
He said the tone taken against Russia had gone beyond what was acceptable even during the Cold War.
The escalation of tension comes as relations between Russia and the West have plunged to their worst level in decades, following the poisoning in March of an ex-spy in England that the UK blamed on Moscow, and alleged Russian interference in the 2016 US election.
The poisoning of Sergei Skripal and his daughter Yulia with what the British government says was a military-grade Novichok nerve agent of a type developed by Russia led to the mass expulsion of Russian diplomats by Western allies, which Moscow responded to in kind.