REUTERS

Obama suggested that Ukraine is not a core U.S. interest -- and that Russia will always be able to maintain dominance in Ukraine because it is a core Russian interest, RFE/RL reports.

Obama rejected the notion that "the decision making of Russia or China” could somehow be influenced by "talking tough or engaging in some military action" in such situations.

Read alsoU.S. "not giving up on Crimea" - VOAHe said such an idea "is contrary to all the evidence we have seen over the last 50 years."

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Obama said 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."

Read also'Enough is enough:' U.S. Senator calls on Russia to release Nadia SavchenkoHe said: "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."