A resolution condemning Syria's violent repression of pro-democracy demonstrations is set to be presented to the UN.
Foreign secretary William Hague told the Commons yesterday that Britain had circulated a draft UN security council resolution.
The joint move with France does not propose any form of military intervention. Instead it calls for the Syrian government to meet their people's legitimate demands, release all prisoners of conscience, lift restrictions on the media and internet and cooperate with the UN high commissioner for human rights.
"A resolution is not in our gift, and needs the support of nine UN security council members and no vetoes," Mr Hague told MPs.
"We are working to persuade other countries that the security council has a responsibility to speak out. President [Bashar] Assad is losing legitimacy and should reform or step aside."
Demonstrations over the weekend saw scores of people killed, while one 13-year-old was allegedly tortured before being killed.
The town of Jisr al-Shughour is bracing itself for a backlash after the Syrian government said 120 of its security personnel had been killed there.
The UN is unlikely to endorse any repetition of an intervention in Syria comparable to that currently underway against Muammar Gaddafi's regime in Libya.
But the UK and France are pressing hard to secure what international pressure they can.
"The situation is now very clear in Syria. The process of reform is dead and we think that Bashar has lost his legitimacy to rule the country," French foreign minister Alain Juppe said.
He admitted that Russia would probably veto "any resolution" about Syria.
"So what to do?" he added.
"We think that now we must go ahead and circulate this draft resolution. We think that it will be possible to get 11 votes in favour of the resolution. Maybe if they see there are 11 votes in favour they will change their mind."