Back in 2008 the Ukraine had already expressed its plans for NATO membership at the NATO Bucharest Summit. Russian Foreign Minister Lavrov and other senior officials have reiterated strong opposition at the time, stressing that Russia would view further NATO eastward expansion as a potential military threat. From Wikileaks (2008):
NATO Enlargement “Potential Military Threat to Russia”
During his annual review of Russia’s foreign policy January 22-23, Foreign Minister Lavrov stressed that Russia had to view continued eastward expansion of NATO, particularly to Ukraine and Georgia, as a potential military threat. While Russia might believe statements from the West that NATO was not directed against Russia, when one looked at recent military activities in NATO countries (establishment of U.S. forward operating locations, etc.) they had to be evaluated not by stated intentions but by potential. …Lavrov emphasized that Russia was convinced that enlargement was not based on security reasons, but was a legacy of the Cold War.
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.
…Ukraine’s gradual shift towards the West was one thing, its preemptive status as a de jure U.S. military ally another.
And so the stage was set for the US to pressure Russia’s strength in the region. What followed was a good old fashioned CIA coup in Kiev, after which 400 elite mercenaries from the notorious US private security firm Academi (formerly Blackwater) joined the Ukrainian military operation against the ethnic-Russian community in Eastern Ukraine. All part of the US its primary objective; to maintain global power and the US dollar hegemony.