They've given up their ground before - voluntarily, as a political concession. But that seems to be over.

After the deaths of 25 people in clashes a day earlier, Ukrainian protesters are prepared to stand and fight again Wednesday.

Police want to clear them out of central Kiev. Some of them died trying to stay put Tuesday - using projectiles and burning barricades to keep security forces at bay at Kiev's Maidan, or Independence Square.

In the aftermath of Tuesday's skirmishes, world leaders ratcheted up calls for sanctions on the Ukrainian government. European Union foreign policy chief Catherine Ashton called the Political and Security Committee into "extraordinary" session to deal with the crisis, while leaders from France, Poland and the United States called for swift action.

U.S. Secretary of State John Kerry was expected to address the issue in remarks later Wednesday in Paris, a senior administration official told CNN. Included in the U.S. approach, the official said: the very real potential of sanctions.

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