Russia demanded Wednesday that the United Nations pledge never to approve foreign intervention in Syria in return for not blocking a resolution calling on President Bashar al-Assad to step down.

The promise is one of five changes Moscow has requested to a draft resolution drawn up by the Arab League which calls on Mr Assad to delegate powers to his deputy, form a unity government and hold free elections.

Britain, the United States and other Western powers have agreed to include a statement that the resolution may not be used to justify military intervention.

A source close to the negotiations said there were problems with the Russians' demand that this clause cover all future resolutions as well.

"We can say we don't want war until we're blue in the face," the source said. "But the fact is that one UN resolution cannot bind future resolutions."

As officials sat down to intensive, line by line negotiations over the draft at the UN in New York, Vladimir Chizhov, the Russian ambassador to the European Union, said it was still "missing the most important thing: a clear clause ruling out the possibility that the resolution could be used to justify military intervention in Syrian affairs from outside".

"For this reason I see no chance this draft could be adopted," he said.

The timetable for putting to the vote what would be the first UN security council resolution on the Syrian crisis has been put back, possibly to early next week. This is regarded as a sign that diplomats believe an accord allowing Russia and China to abstain rather than veto the resolution can be reached.

Sources said Pakistan and India appeared to be coming around to the resolution, putting further pressure on Russia not to wield its veto, although China and South Africa are less warm.

The United States, Britain and France want to back the Arab League's proposal to censure Mr Assad and call for him to step aside.

They are confident that three of the other demands made by Russia - relating to the political transition and the ruling out of arms embargoes and sanctions - can be agreed. A further order, which suggests the issue be looked at again, is seen as pointless.

William Hague, the Foreign Secretary, who urged the UN Security Council on Monday to approve the resolution, denied it would worsen the situation in Syria.

"We have people dying every day," he said. "We have between 30 and 100 people being killed violently every day. We have the torture and abuse of huge numbers of people, including children.

"What the Arab League is putting forward is a plan for a peaceful resolution of this situation."

Meanwhile, the bloodshed in Syria continued, with the Syrian Observatory for Human Rights claiming that 59 people, mostly civilians, were killed.

The Britain-based monitoring group said at least eight civilians died during shelling by regime forces in the restive central city of Homs while 24 were killed in fighting in the Damascus region.

Activists said nearly 200 people had died across the nation in the unrest over the previous three days. France said yesterday that 6,000 people had been killed since the beginning of the uprising nearly 11 months ago.

The latest video screened yesterday on YouTube appeared to show six members of the same family, including children, killed in Homs.