The election of the president in Brussels, likely Friday, is overshadowing the ceremonial aspects of the meeting in Belgium. At stake is leadership of the EU's executive arm, which drafts laws, fines members and negotiates trade deals.
British Prime Minister David Cameron has led a vigorous campaign to block former Luxembourg Prime Minister Jean-Claude Juncker from the presidency, although the prevailing mood among ministers calls for Juncker's election.
Cameron has said nominating Juncker is an "irreversible step which would hand power from the European Council to the European Parliament," the opposite of Cameron's pro-reform European vision in which power is returned to national parliaments.
If it goes to a vote at the meeting, only Hungarian Prime Minister Viktor Orban can be relied upon to side with Cameron. Other EU countries are lining up behind Juncker, a former Eurozone finance minister who worked on emergency bailouts for Greece and Portugal.