Arab countries should push ahead with action to end the violence in Syria, William Hague urged, promising the backing of Western countries after Russia and China blocked United Nations support.

The Foreign Secretary agreed that the two countries had "blood on their hands" and would embolden the Syrian regime in pursuing its deadly crackdown by vetoing a draft resolution.

Moscow and Beijing drew international condemnation for their stance on Saturday, which came hours after a bombardment by security forces of the city of Homs which activists said killed more than 200 people.

But Mr Hague said the setback must not halt efforts to secure a peaceful political transition in Damascus - suggesting Britain could join any Arab League move to sever diplomatic relations.

The international community was "not contemplating military action" however, he declared.

"The main way forward now is for the Arab League to pursue their plan in any case," the Foreign Secretary told the Murnaghan show on Sky News.

"They do not need the permission of the United Nations, although it would have been good to have a clear mandate. They should pursue their plan, they should intensify their own pressure on the Assad regime to stop the killing and allow a peaceful political transition.

"Arab League foreign ministers are meeting in a few days' time. We will be having discussions with some of them and will encourage them very much to intensify their own pressure."

Tunisia has declared that it is withdrawing its recognition of the Assad regime and expelling Syria's ambassador and called on the policy to be adopted more widely by the League.

"Any decision by them to do that would weigh very heavily with us," Mr Hague noted, though he said there were good reasons for trying to maintain a diplomatic presence in the country."