Russia answered the Western pressure with the clear signal that it will continue to provide weapons to the "legitimate" authority in Syria. In so doing, it was sending another message: if you want to have an international "peace" conference, that "legitimate" regime will have to be allowed at the table with no pre-conditions on its participation.
Yet, at the same time, Moscow was not going to wear the villain's mantle designed for it by the "West", but was going to maintain plausible deniability. Th message:
Maybe we are supplying S-300s under an old contract, maybe we are not --- you keep trying to figure it out.
Meanwhile, your move, Washington. Your move, London. Are you really going to pour in more weapons to the insurgency, even as you criticise us for supplying our own to the "legitimate" leaders of Syria?