Russia’s president is challenging the assertion that Syria’s government used chemical weapons against its opponents.
Mr Putin said it would be “utter nonsense” for Syria’s government to provoke opponents with such attacks.
US President Barack Obama says he is considering military action against Syria after intelligence reports that 1,429 people were killed on 21 August.
UN weapons inspectors have left Syria after gathering evidence for four days.
They are taking their samples to the Organisation for the Prevention of Chemical Weapons, in The Hague.
The samples are thought to include soil, swabs from munitions, blood and hair from the victims and, experts say, possibly even flesh from dead bodies.
The US says hundreds of children were among those killed in the suspected chemical weapons attacks, which it blames on the Syrian government.
Syria says the US claim is “full of lies” and says rebels carried out the attacks.