The West has dampened hopes that world powers meeting on Syria on Saturday will find a deal to salvage international envoy Kofi Annan's peace plan to end 16 months of bloodshed and agree on a transition plan for the strife-torn country.
Ahead of the multi-nation talks in Geneva, Britain pointed to persistent opposition from China and Russia to a transition deal, while the United States signalled differences, even though Moscow put up an upbeat front on the meeting.
Foreign ministers of the five permanent Security Council states, the United States, Russia, Britain, China and France, as well as regional powers Qatar, Turkey, Kuwait and Iraq, began arriving for the meeting announced by Annan on Tuesday.
Annan had conspicuously left Iran and Saudi Arabia off the guest list, and circulated a proposal on a "Syrian-led transition" that could help save his peace process that has been largely ignored by both the ruling regime and opposition since it came in force on April 12.
Fighting has only intensified in recent weeks and rights monitors said at least 75 people were killed across the strategic Middle East country on Friday alone.
But a split between western powers and China and Russia emerged as Saturday's meeting drew nearer, over Moscow and Beijing's opposition to Annan's proposal on the composition of an interim Syrian government.
Annan's draft, seen by AFP, envisages power handed to an interim Syrian team that excludes those "whose continued presence and participation would undermine the credibility of the transition and jeopardise stability and reconciliation".
The wording appears to imply -- without saying so directly -- that Syrian President Bashar al-Assad would have to relinquish his grip on power for the idea to succeed.
Russia angrily rejected the suggestion, insisting that Assad's fate "must be decided within the framework of a Syrian dialogue by the Syrian people themselves."
Arriving for talks which were delayed by an hour on Saturday, British Foreign Secretary William Hague said parties had been unable to bridge the gap.
"That remains very difficult and whether it will be possible, I don't know if this will be possible," he said.
Hague stressed that "a stable future for Syria means Assad leaving power."
The US account of a meeting on the eve of Geneva talks between Russian Foreign Minister Sergei Lavrov and US Secretary of State Hillary Clinton also appeared to suggest little agreement on the future of Assad.
A senior US State Department official noted some progress while conceding that "there were still areas of difficulty and difference" between the approaches of Russia and the United States.
"But out of respect to Kofi Annan, they agreed we should all go to Geneva tomorrow to try to produce a result," said the official.
Lavrov took another tack, saying he "detected a shift" in Washington's approach to ending the bloodshed that no longer involved a specific demand for Assad to leave.
"There were no ultimatums. Not a word was said about the document now being discussed in Geneva being completely untouchable," Lavrov told reporters in reference to wording that suggest no future role for Assad.
"I can confidently say that we have a very good chance tomorrow in Geneva to find a common denominator and mark a path forward," Lavrov added.
A conflicting message came from Lavrov's deputy, Gennady Gatilov, who tweeted early Saturday that experts in Geneva had thus far failed to agree to the wording of a final document on Syria because "the Western partners want to determine the political process themselves."
In an editorial published Saturday in Swiss newspaper Le Temps, Annan said that as the "conflict is between Syrians, it is up to the Syrians to resolve it.
"But it would be naive to think that they can, on their own, end the violence today and engage in a real political process."
Regime forces pounded the Damascus suburb of Douma and the central city of Homs on Friday, after one of the bloodiest days of the Syrian uprising in which more than 180 people were thought to have been killed.
Other demonstrations calling for Assad's ouster took place in Aleppo, Daraa, Deir Ezzor, Idlib, Homs and Latakia provinces, while Turkey has sent tanks, troops and missile batteries toward the Syrian border, after Syria shot down a Turkish jet last Friday.
Rights monitors say 15,800 people have perished in the conflict since March last year.