Former Polish prime minister Donald Tusk is pushing the European Union's center of political gravity eastward by taking over the EU presidency from Belgium's Herman Van Rompuy.

Monday's transition ceremony highlighted the increasing power of Poland within the 28-nation EU, and the EU's ongoing shift from a western European economic association half a century ago to a strong political body uniting some 500 million people from Britain to the borders of Russia in the east.

Like Van Rompuy before him, Tusk will be in charge of EU summits of government leaders who meet about four times a year to set out long-term goals or deal with short-term crises like the financial problems over the past years and the fighting in Ukraine this year.