European Union leaders were expected to discuss possible sanctions against Belarus as they convened on the second day of a summit in Brussels.
The gathering comes after the Belarusian government this week told the Polish and EU ambassadors to leave Minsk and recalled its own envoy from Brussels in response to new EU sanctions targeting Belarusian judges and police.
EU leaders reportedly plan to express "serious and deepening concern" over the deteriorating human rights situation in Belarus.
EU leaders are also expected to announced a decision should be made in September on whether to allow Bulgaria and Romania into the Schengen border-free area.
Twenty-five of the EU's 27 members -- excluding Britain and the Czech Republic -- will also sign a new agreement giving the EU greater oversite over national budgets.
The EU granted Serbia candidacy status on March 1.
Based on dpa reporting