The interests between the West and Russia diverge significantly in Syria. There is common ground e.g., reducing the intensity of the conflict or bringing an end to it. But as to the preferred outcome i.e.., who governs or a no fly zone, the differences are deep. On the former, Russia has a major interest in maintaining its strategic warm water port naval facility. Just as the anti-Assad forces have never provided credible and concrete information concerning future governance, the role of ethnic/religious minorities, and overall foreign policy parameters, they have provided nothing concrete for Russia to expect that it could retain its naval facility should they gain power. On the latter, the stretching of the mandate set forth in UNSC Res. 1973 (2011) of Libya's no fly zone into a mechanism for regime change has led Russia to automatically oppose such devices. Russia did not support the mandate change and does not believe that it can trust parties to respect limited mandates given to such mechanisms. Once credibility is shattered--and credibility related to the purposes of such devices has been shattered as mutual confidence is lacking--it takes a long time to rebuild it.
In short, Russia will agree when it comes to trying to devise a diplomatic process or negotiations for reduce the intensity of the sectarian conflict, reach a ceasefire, and perhaps negotiate a long-term solution. It won't agree with demands that the long-term solution be regime change (though if the parties accept it at the bargaining table, that's a different matter, but the battlefield situation may preclude agreement on such an outcome if talks even occur) or a no fly zone. It will also likely respond to Western arms deliveries with a step-up of its own arms deliveries.
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