Russia should not block the UN's efforts to pass a resolution denouncing Syrian leader Bashar al-Assad, Downing Street said on Monday.
In a stern warning, a Number 10 spokesperson said Russia could not explain "blocking" the UN or "providing cover for the regime's brutal repression."
It comes as William Hague plans to travel to New York to support a draft resolution in the UN calling on Bashar al-Assad to step down as Syrian leader. The head of the Arab League Nabil Elaraby will als0 brief the UN Security council on the situation in Syria.
The resolution was drafted after the Arab League suspended their mission in the country, following increased violence and reports that the army had re-taken control of some parts of Damascus suburbs held by rebels.
But Russia's Deputy Foreign Minister Gennady Gatilov has said security council members should "study the recommendations and conclusions of the observer mission in detail," in a sign the resolution will take longer to agree.
A Downing Street spokesperson said: "There is hope to agree a UN Security Council resolution this week and to make it very clear to President Assad and his regime that the killing must stop.
"We've been working in New York to support a text drafted by Arab members of the Security Council, which promotes a regional approach to the crisis."