(LISBON) - Portuguese President Anibal Cavaco Silva officially ratified the EU's reforming Lisbon treaty on Friday, symbolically choosing 'Europe Day' to do so.

The treaty, signed by European leaders in the Portuguese capital last December, was formally promulgated at a solemn ceremony following its approval by the national parliament last month.

The treaty constitutes "a step forward towards the construction of a more unified Europe, one more in solidarity," said Cavaco Silva.

Its success "shows the political determination and the convergence of the efforts of the leaders of the member states and the European institutions," he added.

Austria, Bulgaria, Denmark, France, Hungary, Lithuania, Latvia, Malta, Poland, Portugal, Romania, Slovakia and Slovenia have now ratified the treaty, according to the EU's executive body, the European Commission.

All 27 EU member states must do so before it can come into effect, as planned, next year.

Only Ireland is constitutionally bound to put the treaty to a national referendum which it will do next month.

The treaty is deemed essential to streamline the workings of the European bloc, which has boosted its ranks from 15 to 27 member states since 2004.

It also introduces the post of an EU president, one of the factors which eurosceptics point to as an indication of the movement towards a federal Europe.

Numerous celebrations were scheduled for late Friday throughout Portugal to mark Europe Day, which commemorates the May 9, 1950 declaration by then French foreign minister Robert Schuman which is considered the founding proposal for the European Union.

In Lisbon itself European Commission chief Jose Manuel Barroso, who is Portuguese, was handed the keys of the capital.

Barroso's work at the head of the EU's executive arm "constitutes an honour for Portugal and for the city of Lisbon," said Mayor Antonio Costa.

Europe Day was also marked elsewhere, with a 12-metre high model of a European Ariane 5 rocket set up next to stands of regional European products at the Hotel de Ville, town hall, in Paris. A cinema chain in the French capital showed 27 films in their original languages, one from each EU member state.

In Marseille, southern France, a "European village" was set up for a grand picnic with the European anthem, Beethoven's Ode to Joy, ringing out from a local theatre.

In The Hague a "Europe Night" was planned for the youth market, while in Brussels, the seat of the European Union, the day was marked by a holiday for all the EU institutions.

In the landmark 1950 address, Schuman called on France, Germany and other European nations to work towards what became the European Coal and Steel Community, the start of the European project following the devastation of World War II.

A European summit in 1985 decided to commemorate this event each year as Europe Day.

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