Ukrainian resistance and logistical problems are hampering Russian troops, who have not yet taken any big Ukrainian cities, say U.S. and U.K. officials.
Russia has run into tougher resistance than it anticipated from Ukraine, but Moscow still has "significant combat power" at its disposal, a U.S. official said.
The United States will impose a slate of sanctions on Russian President Vladimir Putin and Foreign Minister Sergey Lavrov, the White House said Friday.
European stocks closed higher on Friday, bouncing back from a sharp sell-off as market participants assessed the impact of Western sanctions against Russia.
In the hours after Russia invaded Ukraine, the U.S., U.K. and European Union announced new sanctions aimed at isolating Moscow from the global economy.
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