The Russian foreign ministry claimed its expert findings show that the chemical weapon used in the chemical attack in Syria are similar to ones made by a rebel group. President Putin has warned the West against taking one-sided action in Syria.
President Vladimir Putin said Russia had provided some components of the S-300 air defence missile system to Syria but had frozen further shipments.
He suggested that Russia may sell the missile systems elsewhere if western nations attack Syria without UN Security Council backing.
In an interview with The Associated Press and Russia's state Channel 1 television, he said: "We have a contract for the delivery of the S-300s. We have supplied some of the components, but the delivery hasn't been completed. We have suspended it for now.
"But if we see that steps are taken that violate the existing international norms, we shall think how we should act in the future, in particular regarding supplies of such sensitive weapons to certain regions of the world."
The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.