U.S. President Barack Obama on Wednesday again called for Russia to de-escalate the situation in Ukraine -- and warned of further isolation and "costs" if Moscow doesn’t respond to the West’s call for a change of course.

U.S. President Barack Obama on Wednesday again called for Russia to de-escalate the situation in Ukraine -- and warned of further isolation and "costs" if Moscow doesn't respond to the West's call for a change of course.

The United States and Europe are united in their support for Ukraine, including the need for economic assistance, and in their efforts to isolate Russia for its intervention in Crimea, Obama said, speaking at an European Union-U.S. summit in Brussels, Belgium.