Turkey's application to accede to the European Economic Community, the predecessor of the European Union (EU), was made on 14 April 1987. Turkey has been an associate member since 1963. After the ten founding members, Turkey was one of the first countries to become a member of the Council of Europe in 1949, and was also a founding member of the Organisation for Economic Co-operation and Development (OECD) in 1961 and the Organization for Security and Co-operation in Europe (OSCE) in 1973. The country has also been an associate member of the Western European Union from 1992 to its end in 2011, and is a part of the "Western Europe" branch of the Western European and Others Group (WEOG) at the United Nations. Turkey signed a Customs Union agreement with the EU in 1995 and was officially recognised as a candidate for full membership on 12 December 1999, at the Helsinki summit of the European Council. Negotiations were started on 3 October 2005. The membership bid has become a major controversy of the ongoing enlargement of the European Union.