, William Hague and Alain Juppé are due at the UN security council in New York on Tuesday to support an Arab League plan to end the violence in Syria and to try to overcome Russian-led opposition to a UN-backed demand for political change in Damascus.
As Syrian forces poured into Damascus districts to wrest them from rebel control, a joint European-Arab resolution calling for to hand power to his deputy as a prelude to political transition won the support of the 10 security council member states necessary to force a vote.
Diplomats at the UN said that a vote on the resolution, formally presented by Morocco, was likely by Thursday, after the council considers a report on the Syrian situation by the Arab League secretary general, Nabil Elaraby, and the Qatari prime minister, Hamad Bin Jassim, on Tuesday followed by an ambassadors' meeting on Wednesday aimed at finding a compromise formula acceptable to Russia, Assad's principal supporter on the world stage.
"We believe the UN must act to support the people of and that Russia can no longer explain blocking the UN and providing cover for the regime's brutal repression," a Downing Street spokeswoman said.
Juppé's spokesman, Bernard Valero said: "The goal of tomorrow's ministerial meeting is to ensure that the security council has an opportunity to listen to the report by the Arab League, which has been involved on the ground since the end of December, and that it is able to support its efforts and recommendations."
Moscow, which has threatened to veto the security council resolution, views it as a western-backed attempt to open the door to military intervention. The Russian foreign ministry announced on Monday that the Syrian government had accepted an invitation to peace talks, but the opposition National Syrian Council told Reuters it had not been asked and would not take part.
Opposition groups inside Syria, spearheaded by the irregular forces of the Free Syrian Army, claimed to have made a tactical withdrawal from the areas, mainly on Damascus's northern outskirts, which they took control of over the weekend, as Syrian forces moved in and have vowed to mount more guerrilla-style operations as their campaign against Assad's regime enters a new phase.
They say the aim of the weekend forays was to demonstrate that the capital was no longer an impregnable regime stronghold, but buffeted from the escalating violence now rife in many of Syria's other towns and cities.
The soaring death toll in Damascus and across the country suggests that the fighting has indeed reached levels rarely witnessed during the 10-month uprising.
More than 60 people, including loyalist troops, are believed to have been killed nationwide on Sunday and at least 30 more deaths were reported by early afternoon on Monday as both sides stepped up offensives.
Around 6,000 civilians and defectors, some of whom had taken up arms, are thought to have been killed during the crisis. Syria says at least 2,000 of its security forces have lost their lives.
Opposition groups claim that the checkpoints they set up in the north and east of the capital late last week will be re-established once regime tanks and armoured vehicles are redeployed. Tanks have been stationed in suburbs as close to six miles from the heart of Damascus, one activist told the Guardian.
They have also been deployed in the second city and commercial hub of Aleppo, which has remained largely immune from mass demonstrations or violence since the anti-regime uprising began last March.
Fighting has broken out to the north and east of the capital, with opposition militias claiming to have destroyed military vehicles on the road to Damascus airport.
Elsewhere in the country, an intensive regime offensive continues in the city of Homs, which has been violently contested by both sides since demonstrations there morphed into a full-blown insurgency late in the summer.
Continued heavy clashes are also taking place in the nearby city of Hama and in Idlib in the north-west, where loyalist forces have been engaged in pitched battles with defectors who have struggled to establish a command-and-control structure.
Although attempts have been made by Arab and European states to organise the Free Syrian Army, it remains largely a series of franchises answerable to a loose command and with only limited means to tackle the Syrian military head-on.
Defections from the upper echelons of the military remain rare. One of the highest-profile defectors, Lieutenant Colonel Hussein Harmoush, is reported by several human rights organisations to have been executed by firing squad last week after mysteriously disappearing from the safe haven of a refugee camp in southern Turkey.