"The European Union (EU) has long viewed the enlargement process as an extraordinary opportunity to promote political stability and economic prosperity in Europe. Since 2004, EU membership has grown from 15 to 27 countries, bringing in most states of Central and Eastern Europe and fulfilling an historic pledge to further the integration of the continent by peaceful means. Analysts contend that the carefully managed process of enlargement is one of the EU's most powerful policy tools, and that, over the years, it has helped transform many European states into functioning democracies and more affluent countries. The EU maintains that the enlargement door remains open to any European country that fulfills the EU's political and economic criteria for membership. At the same time, EU enlargement is also very much a political process; most all significant steps on the long path to accession require the unanimous agreement of the existing 27 member states. As such, a prospective EU candidate's relationship or conflicts with individual member states may also influence a country's EU accession prospects and timeline. […] Successive U.S. Administrations and many Members of Congress have long backed EU enlargement, believing that it serves U.S. interests by advancing democracy and economic prosperity throughout the European continent. Over the years, the only significant U.S. criticism of the EU's enlargement process has been that the Union was moving too slowly, especially with respect to Turkey, which Washington believes should be anchored firmly to Europe. Some U.S. officials are concerned that 'enlargement fatigue' as well as the EU's ongoing financial crisis could hinder EU expansion."
CRS Report for Congress, RS21344