"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 28 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. Croatia is the EU's newest member, acceding to the EU on July 1, 2013. 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 28 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. […] The status of EU enlargement and its implications for both the EU itself and U.S.-EU relations may be of interest to the 113th Congress. For additional information, see also CRS [Congressional Research Service] Report RS21372, 'The European Union: Questions and Answers,' by Kristin Archick; and CRS Report RS22517, 'European Union Enlargement: A Status Report on Turkey's Accession Negotiations,' by Vincent L. Morelli."
CRS Report for Congress, RS21344