Secretary Hague: Ukraine Crisis biggest in 21st Century Europe

The Russian warning came as British Foreign Secretary William Hague on Monday called the standoff in Ukraine the "biggest crisis in Europe of the 21st century."
In Washington, President Obama said Russia is "on the wrong side of history'' by intervening in Ukraine. He said he is considering diplomatic and economic steps to isolate Moscow.
"Over time this will be a costly proposition for Russia, and now's the time for them to consider whether they can serve their interests in a way that resorts to diplomacy as opposed to force," Obama said from the Oval Office.
The U.S. originally estimated that 6,000 Russian troops were dispatched to Crimea, but Ukraine's mission to the United Nations said Monday that 16,000 had been deployed. That stoked fears that the Kremlin might carry out more land grabs in pro-Russian eastern Ukraine.
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Report: Putin calls troops back from military exercises