Russia's foreign minister has lashed out at the west's "blind and ideological" approach to the Syrian conflict, and said that both the regime and the rebels hold chemical weapons and should hand them over.
Sergey Lavrov said the US and its allies are "cunning" when contending that only the troops of Bashar al-Assad have stockpiles of chemical weapons.
Lavrov claimed rebels have their own laboratories where they make lethal sarin-like gasses, and cited Israeli intelligence reports that groups fighting Assad had at least twice seized areas where government chemical weapons were stored.
"When our western partners repeatedly say that only the regime has weapons and that's why only the regime could have used them, and the opposition has no chemical weapons, they are cunning," Lavrov told Russian Channel 1 television.
"According to our estimates, there is a strong probability that in addition to home-grown labs in which militants are trying to cook up harmful and deadly concoctions, the data provided by the Israelis is true.
"Those who fund and sponsor opposition groups - including extremists - [should] demand that they hand over the [arms] that have been seized so that they can be destroyed," Lavrov said.
Russia has long maintained rebel groups and not the regime are to blame for a gas attack in the Damascus suburb of Ghouta that left more than 1,400 people dead in August.
Western government and human rights organisations lay the blame on Assad instead, and the US has threatened to launch a punitive military strike against the regime over the massacre.
The operation has been put on hold following Russia's diplomatic intervention, as the Kremlin convinced the regime to handover its chemical stockpiles.
Lavrov has now accused the US of using the deal as a pretext for a UN resolution allowing the use of force.
The United States, France and Britain have been pressuring Russia to embed the agreement in a Security Council resolution threatening military intervention in case of Syrian non-compliance.
"Our partners are blinded by an ideological mission for regime change," said Lavrov. "They cannot admit they have made another mistake.
"They see in the US-Russian deal not a chance to save the planet from significant quantities of chemical weapons in Syria, but as a chance to ... push through a resolution involving [the threat of] force against the regime.
"I am convinced that the west is doing this to demonstrate that they call the shots in the Middle East. This is a totally politicised approach."
Lavrov also said that Russia is ready to send military observers to Syria to provide security for efforts to eliminate chemical weapons.
"We are ready to share our servicemen and military police to participate in these forces," Lavrov said, ruling out sending a full military contingent.
"It seems to me that military observers will be sufficient," he said.