One day after Syrian rebels killed top aides to President Assad in the heart of Damascus, Security Council members China and Russia have vetoed a resolution extending the UN Observer Mission. America's Ambassador to the UN, Susan Rice said that history would "judge harshly" the Council's failure "from assuming even its most basic responsibilities." President Bashar al-Assad appeared today on Syrian TV, swearing in a new defense minister to replace the one killed yesterday. But violence has escalated in capital city, and there are real questions about his regime's capacity to survive. Reporter Liz Sly is based in Turkey for the Washington Post.