“The mere fact of the timing when you consider what is going on in Ukraine and you see the sudden nature of the exercise would cause concern,” this official said. “From an intelligence perspective we don’t have any reason to think it’s more than military exercises."

http://www.thedailybeast.com/articles/2014/02/27/u-s-spies-no-russia-isn-t-about-to-invade-ukraine.html