Mentrestant, els Estats membres negociaven el nou Tractat de la Unió Europea, que va ser adoptat pel Consell Europeu (els caps d’Estat i de Govern) a Maastricht al desembre de 1991.
At the same time, the member states were negotiating the new Treaty on European Union, which was adopted by the European Council, composed of presidents and/or prime ministers, at Maastricht in December 1991.