Moscow, which has spooked the West with a troop buildup near Ukraine, last week unveiled a wish list of security proposals it wants to negotiate, including a promise NATO would give up any military activity in Eastern Europe and Ukraine.

Washington has said some of Russia's proposals are obviously unacceptable, but that the United States will respond some time this week with more concrete proposals on the format of any talks.

Russia’s Deputy Foreign Minister Sergei Ryabkov said that Moscow had so far received no response from the United States.