Sen McCain made a statement on the Ukraine Crisis about an hour ago (reported by the BBC):

Every moment that the United States and our allies fail to respond sends the signal to President Putin that he can be even more ambitious and aggressive in his military intervention in Ukraine. There is a range of serious options at our disposal at this time without the use of military force. I call on President Obama to rally our European and NATO allies to make clear what costs Russia will face for its aggression and to impose those consequences without further delay.