Former Polish prime minister Donald Tusk has taken over the European Union presidency from Belgium's Herman Van Rompuy.

The 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.

With unemployment still hovering around record levels and underscoring a deep economic divide in the EU, Mr Tusk said Europeans "need ruthless determination to end the economic crisis".

He has long kept an eye on Russia and sees the conflict in Ukraine and testy relations with Moscow, especially for nearby states like the Baltic nations, as a key challenge during his tenure.

"Europe has to secure its borders and support those in the neighbourhood who share our values," Mr Tusk said. In standing up to Russia, he has a key ally in the United States and he said the trans-Atlantic relationship is second to none in international politics despite the acrimony over revelations of surveillance by the US National Security Agency of European allies.

The year ahead will be crucial," Mr Tusk said. "Relations between Europe and the United States are the backbone of the community of democracies."