European Union leaders on Saturday chose Polish Prime Minister Donald Tusk to chair the European Council and named Italian Federica Mogherini to run the bloc's foreign relations as it prepared to threaten Russia with new sanctions over Ukraine.

A summit in Brussels shared the two coveted EU posts between a Kremlin critic from ex-communist Eastern Europe and the foreign minister of one of Moscow's biggest customers for gas. EU officials gave Ukraine's embattled President Petro Poroshenko a warm welcome and assurances of further support.

But divisions among the 28 EU nations have hampered action against Moscow, and a draft of the final statement indicated that they will merely ask the bloc's executive arm "urgently" to prepare more options for sanctions. Discussion on the measures lasted beyond midnight.