Current CIA Director William Burns in 2008, leaked Wikileaks cable revealed by Julian Assange:

'Ukraine and Georgia’s NATO aspirations not only touch a raw nerve in Russia, they engender serious concerns about the consequences for stability in the region. Not only does Russia perceive encirclement, and efforts to undermine Russia’s influence in the region, but it also fears unpredictable and uncontrolled consequences which would seriously affect Russian security interests. Experts tell us that Russia is particularly worried that the strong divisions in Ukraine over NATO membership, with much of the ethnic-Russian community against membership, could lead to a major split, involving violence or at worst, civil war. In that eventuality, Russia would have to decide whether to intervene; a decision Russia does not want to have to face.'