Barack Obama expressed doubts that one can’t influence on making decisions in such countries as Russia or China by decisive announcements or even military actions (Radio Liberty).
He said such an idea "is contrary to all the evidence we have seen over the last 50 years."
Obama added there are "ways to deter, but it requires you to be very clear ahead of time about what is worth going to war for and what is not." "If there is somebody in [Washington] that would claim that we would consider going to war with Russia over Crimea and eastern Ukraine, they should speak up and be very clear about it."
"Putin acted in Ukraine in response to a client state that was about to slip out of his grasp. And he improvised in a way to hang on to his control there," the U.S. president explained his understanding of the actions of the Russian president in Crimea and the Donbas. "He's done the exact same thing in Syria, at enormous cost to the well-being of his own country," the U.S. President said.