At the moment I think Russia will occupy the whole of Ukraine and so I think the best would be if the Ukraine attack the NATO.
The NATO can then marching into the Ukraine and occupy the areas which are not be part of the Separatists.
Thus, the attack of the separatists would be stopped.....
I mean a declaration of war and not a real fighting between Ukraine and NATO.
http://www.reuters.com/article/2015/02/20/us-russia-putin-military-idUSKBN0LO1NQ20150220
