European Union leaders meet on Friday and Saturday to try to finalise a first constitution for an enlarged bloc, due to expand from 15 to 25 states next May.

Here is a short chronology of the major treaties which formed the European Union and its forerunners.

¤ April 18, 1951: The treaty to create a European Coal and Steel Community (ECSC) is signed in Paris. Belgium, France, Italy, Luxembourg, the Netherlands and West Germany agree to place their coal and steel industries under a common authority.

¤ March 25, 1957: The same six countries sign treaties to create the European Economic Community (EEC) and the European Atomic Energy Community (Euratom).

The EEC Treaty of Rome aims to eliminate tariffs, quotas and other trade barriers between member countries and guarantee that persons, services and capital can move freely across borders.

The Euratom treaty aims to promote the use of nuclear energy for peaceful purposes.

¤ April 8, 1965: The six countries sign the Merger Treaty to merge the executive institutions of the ECSC, EEC and Euratom, creating the European Community. It came into effect on July 1, 1967.

¤ Jan 1, 1973: Britain, Denmark and Ireland join the Community, taking membership to nine. Norway votes not to join.

¤ Jan 1, 1981: Greece becomes the 10th member.

¤ Jan 1, 1986: Spain and Portugal join.

¤ Feb 1986: EC countries sign the Single European Act that amends the EC treaties to speed up decision-making and facilitate the drive to create a border-free single market, expanding the use of majority voting.

¤ Nov 1, 1993: The Treaty on European Union, agreed in the Dutch town of Maastricht in Dec 1991, comes into force. The treaty establishes a new European Union, embracing the EC and its 12 member states.

It calls for the creation of a single currency by 1999 and the development of a common foreign and security policy, while giving the European Parliament veto power over some legislation.

¤ Jan 1, 1995: Austria, Finland and Sweden join the European Union.

¤ March 26, 1995: EU members France, Germany, Belgium, Luxembourg, the Netherlands, Spain and Portugal sign the Schengen agreement to drop border controls with each other.

¤ June 1997: The Amsterdam Treaty amends the Treaty of the European Union agreed at Maastricht, creating the role of High Representative for Foreign and Security Policy.

¤ Dec 2000: The Nice Treaty, agreed at an acrimonious marathon summit, paves the way for the bloc's eastern enlargement.

¤ Dec 2002: EU leaders meeting in Copenhagen agree to admit 10 new members - Poland, Hungary, the Czech Republic, Slovakia, Slovenia, Estonia, Latvia, Lithuania, Cyprus and Malta - in May 2004.

¤ Jan 31, 2003: The Nice Treaty comes into force. Its complex weighted voting system only applies from Jan 1, 2005.

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