A few more massacres like the one in Houla last weekend and Russia will be in a very lonely place internationally.
China and Russia, which both wield a veto at the UN Security Council, have blocked two previous resolutions calling for tougher action on Damascus.
On Tuesday, French President Francois Hollande said military intervention authorised by the Security Council had not yet been ruled out. The US state department expressed hope that the events in Houla might prove a "turning point in Russian thinking".
Russian Deputy Foreign Minister Gennady Gatilov said: "We have always said that we are categorically against any outside interference in the Syrian conflict because this will only exacerbate the situation for both Syria and the region as a whole."
A spokesman for China's foreign ministry also reiterated Beijing's opposition to military intervention in Syria or forced "regime change".
Syria's main opposition group, the Syrian National Council, said Russia had chosen "to join ranks with the Syrian regime and to provide it with political cover", AFP news agency reports.
With the west expelling Syrian ambassadors, Russia and China now find themselves hard pressed to continue justifying their obstructionism. The world is probably not going to intervene in Syria militarily, but isolating Assad and anyone who stands with him is a definite possibility. A blockade is not out of the question, nor is establishing no-fly zones. But ground troops - even to create a "humanitarian corridor" - is not in the cards nor is any massive intervention to overthrow Assad.
Failing that, Assad has the continued support of his Alawite mafia as well as the military. As long as he holds those two cards, he is probably going to remain in power.