The EU leaders started Thursday the most significant summit of the bloc since French and Dutch voters rejected the draft European Constitution two years ago.
The negotiations are expected to be extremely tense. They will be focused on agreeing a new "reform treaty" to replace the EU constitution.
The new treaty abandons the term "constitution" and will simply amend two existing EU treaties, according reports.
However, the chances of deal are thought to be low with Polish and British objections threatening to scupper any agreement.
German chancellor Angela Merkel call on the leader of the 27th member countries to put for discussion all the questions topical in the countries they represent.
Prime Minister Sergey Stanishev represents Bulgaria in the European Council of heads of states and governments of EU member states and acceding countries.