When a person takes off his glasses in the middle of a conversation, press conference, cross-examination, etc. it is a sign they are stalling for thinking-time. In a negotiating or mediating type setting, this is most often seen at the end of the discussion when a decision has been asked for. It is also one of examples of a pacifier, also known as a manipulator or adaptor. Like all manipulators, it is a sign of increased discomfort or anxiety.
Although highly refined and very experienced in high pressure situations, we can be sure that Russian Deputy Prime Minister Sergei Ivanov feels anxiety and is stalling for time while he is formulating his answer. Remember this the next time you are in a negotiation.