Mindful the conflict may be far from over, Britain has urged fellow European Union states to lift an arms embargo, arguing it would strengthen those rebel groups favoured by Western powers.
Visiting Moscow after Israel bombed sites near Damascus and as President Barack Obama also faces renewed calls to arm the rebels, US Secretary of State John Kerry said late on Tuesday that Russia agreed to work on a conference in the coming weeks.
An East-West disagreement that has seen some of the frostiest exchanges between Washington and Moscow since the Cold War has deadlocked UN efforts to settle the Syrian conflict for two years, so any rapprochement could bring an international common front closer than it has been for many months.
Israeli air strikes, reports of the use of chemical weapons and the increasing prominence of al Qaeda-linked militants among the rebels have all added to international urgency for an end to a war that has killed more than 70,000 people.
UN Secretary-General Ban Ki-moon on Wednesday welcomed the announcement by Kerry and Russian Foreign Minister Sergei Lavrov.
“The Secretary-General and Joint Special Representative (Lakhdar) Brahimi have asserted from the outset their conviction that a negotiated political solution is the only way to end this prolonged and ever-deepening crisis, the UN statement said.
But with Syria's factional and sectarian hatreds more entrenched than ever, it is far from clear the warring parties are ready to negotiate with each other. Most opposition figures have ruled out talks unless Assad and his inner circle are excluded from any future transitional government.
“I believe the opposition would find it impossible to hold talks over a government that still had Assad at its head,” said Samir Nashar of the opposition's umbrella National Coalition.
“Before making any decisions, we need to know what Assad's role would be. That point has been left vague, we believe intentionally so, in order to try to drag the opposition into talks before a decision on that is made.”
In the past, the United States has backed opposition demands that Assad be excluded from any future government, while Russia has said that must be for Syrians to decide, a formula the opposition believes could be used to keep Assad in power.
Opposition members said they were concerned by comments from Kerry in Moscow, echoing Russia that the decision on who takes part in a transitional government should be left to Syrians.
“Syrians are worried that the United States is advancing its own interests with Russia, using the blood and suffering of the Syrian people,” said National Coalition member Ahmed Ramadan.
Inside Syria, where rebel groups have disparate views, a military commander, Abdeljabbar al-Oqaidi, told Reuters, “If the regime were present, I do not believe we would want to attend.”
There was no immediate response from the Syrian government, which has offered reforms but dismisses those fighting it as terrorists and puppets of outside powers - the West, Turkey and Arab states opposed to Assad’s ally Iran.
