This is a very different situation from a government inviting in UN peacekeepers. First the Russians are an involved party – part of the cause of the conflict due to the protests in Kiev first breaking out due to Yanukovych turning from the EU to Russia a country so involved would never be asked to be involved in a UN peacekeeping force. Secondly a UN peacekeeping force requires not only the approval of the government but of the UN Security Council. [1] This has not been forthcoming in this case.  On the other hand it is different from basing in another country as the US does as that does not involve coercion. Or for that matter taking vital strategic points such as airports and surrounding the host countries military bases. [2]  [1] ‘Role of the Security Council’, United Nations Peacekeeping, accessed 4/3/2014  [2] Fraser, 2014