Britain, France and the United States have condemned a decision by Russia and China to veto a UN Security Council resolution that would have imposed non-military sanctions on the government of Syrian president Bashar al-Assad.

It was the third time that Moscow and Beijing have thwarted efforts by the west to move against Assad since the uprsing erupted in Syria almost 17 months ago.

UK Foreign Secretary William Hague called their veto inexcusable and indefensible.

They have turned their back on the people of Syria in their darkest hour, he said.

Russia's UN ambassador Vitaly Churkin responded that the sanctions under question would have led to external military involvement in Syrian domestic affairs.”