One by one, President Barack Obama's warnings to Russia are being brushed aside by President Vladimir Putin, who appears to be speeding up efforts to formally stake his claim to Ukraine's Crimea peninsula.


Cossacks stand guard at the entrance to the Crimean Parliament building in Simferopol, Ukraine. (Sean Gallup/Getty Images)

In the week since Obama declared there would be "costs" if Putin pressed into Crimea, Russian forces have taken control of the region and a referendum has been scheduled to decide its future.

Obama declared the vote a violation of international law, but in a region where ethnic Russians are the majority, the referendum seems sure to become another barrier to White House efforts to compel Putin to pull back in Crimea.

If Crimea votes to join Russia, the referendum could also put Obama in the awkward position of opposing the outcome of a popular vote.

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