BRUSSELS, Dec. 14 (Xinhua) -- One day after signing a landmark treaty in Lisbon, leaders of the European Union (EU) member states were here Friday to attend a one-day summit.

    The following is background information about the EU summit.

    The EU summit gathers the heads of state and government within the EU, together with the president of the European Commission. It is a synonym for the European Council, the supreme decision-making body of the 27-member bloc.

    Dubbed as a "supreme political authority," the EU summit has the power to lead in foreign policy, ratify important documents and negotiate treaty changes.

    The summit is chaired by the EU's rotating presidency, however, according to the newly-signed Lisbon Treaty, the EU will soon have an elected president, replacing the current six-month rotating presidency. The elected EU president will serve a renewable term of two-and-a-half years.

    The first EU summit took place in February 1961, and was held irregularly throughout the 1960s. The summits were only formalized in 1974, at the December one in Paris, following a proposal from then-French President Valery Giscard d'Estaing.

    The EU summit is held at least twice a year, although in recent years it has been held around four times annually.

    During the first half of this year, the German Presidency hosted two formal summits, one informal summit in Berlin to mark the 50th anniversary of the Rome Treaty, and one "mini summit" in Portugal.

    After Portugal took the presidency in July, it held one informal summit in Lisbon in October, at which the Lisbon Treaty was hammered out.

    Throughout its history, the EU summit has always been held in the EU member state holding the rotating presidency.

    Starting from 2002, the venue of the EU formal summit was formalized, and has been held in Brussels. However, the EU member state holding the EU presidency may arrange one or two informal summits in its own territory.

    There had been contention as to where to hold the last EU summit of this year.

    Portugal insisted that the new EU reform treaty, negotiated in Lisbon, should also be signed there, thus making the landmark document the Lisbon Treaty.

    But the Belgian government, keen not to set a precedent, had insisted that the actual summit take place in Brussels as usual.

    As a result, EU leaders had to fly to Lisbon Thursday to sign the treaty and then return to Brussels to continue with normal business Friday. This attracted protests from environmental groups, who accused the EU of hypocrisy for demanding lower carbon emissions while flying across Europe for the same summit for political reasons.