David Cameron joined Barack Obama yesterday in warning the Syrian regime that any use of chemical weapons would be "unacceptable" and hinted that it could prompt Western military intervention.
Western leaders – criticised for failing to find a solution to the civil war, which has claimed 17,000 lives – have conceded that diplomatic efforts to end the crisis have been stymied by countries such as Russia which are keen to avoid Washington and London gaining leverage in Syria.
However, after speaking on the telephone in recent days, the Prime Minister and President Obama apparently agree that the deployment of chemical or biological weapons by the government in Damascus "would force them [the West] to revisit their approach so far", according to a Downing Street spokeswoman.
It is widely accepted that Syria possesses such weapons, and reports that jihadist elements have joined the effort to remove the Syrian government will have sounded alarm bells in London and Washington that such groups could get their hands on the weapons in the event that the government of Bashar al-Assad suddenly collapses.
A spokesman for the Russian foreign ministry said Moscow has guarantees from the Syrian government that it will not use or move its chemical weapons.
The Syrian army is desperately trying to retake areas it has lost in recent weeks, most notably in the second city of Aleppo, which has been the scene of some of the heaviest fighting. Reports yesterday suggested there was heavy shelling in the rebel-held Saif al-Dawla district.
Britain has firmly backed the rebels and has formally announced financial assistance in the form of communications and medical equipment, despite ruling out the deployment of troops or the provision of weapons to the Free Syrian Army (FSA). Reports at the weekend suggested Britain is also providing the FSA with intelligence about Syria's regular army.