Heads of State or government from 25 member states of the European Union (EU) signed the EU Constitution treaty, the bloc's first Constitution, at Campidoglio of Rome on Friday.

Belgium became the first to sign this historic document as the arrangement is done by alphabetic order. Each member states sent two leaders, the president or the prime minister plus the foreign minister, to sign the pact.

The signing of the treaty took place in the Ala Degli Orazi and Curiazi of Campidoglio, the same room in which the six original member countries -- France, Germany, Italy, the Netherlands, Belgium and Luxembourg -- signed the Treaty establishing the European Community on March 25, 1957.

The signing lasted around half an hour and after that the leaders took a group photo under a ring-shaped logo of "European Union" in Latin language with the EU flag and the national flags of the member states.

The whole signing ceremony was live broadcasted across Europe and over 400 EU citizens could watch this historic event.

Together with the 25 leaders, heads of state or government from Turkey, Bulgaria and Romania, the EU's three candidate countries, signed the Final Act establishing a Constitution for Europe, a document specifying the conclusion of the talks on the Constitution, in which the three countries had also participated.

Croatia, an applicant country for EU membership, was invited to attend the signing ceremony to witness this historic event for European integration.

Addressing the signing ceremony, EU leaders hailed this milestone event, recalled the history of European integration and expressed confidence for the prospects of European integration.

"Today's proceeding thus marks a historic date: Europe has at last acquired a Constitution based on the twofold and indivisible consensus of the citizens and the Member States," said host Italian Prime Minister Silvio Berlusconi, who opened the Intergovernmental Conference for the Constitutional talks in October of 2003 as the EU Presidency.

Irish Prime Minister Bertie Ahern, who led to finalize the EU Constitution in June of this year, shed tears with excitement when "Ode to Joy" , the EU's anthem, was played to mark the conclusion of the event.

"We face the future with optimism and determination. Enlargement is an inspiration for the EU," he said.

Some other leaders were cautious on the future of European integration though they warmly praised the treaty.

"The signing of the European Constitution does not mean we have crossed the finishing line," warned outgoing European Commission President Romano Prodi, who will remain in the post due to Jose Barroso withdrew his lineup to the European Parliament on Wednesday.

"In the months ahead the Governments of the Union's 25 member states will need to use their best endeavors to persuade their parliaments and citizens to ratify the new Constitutional treaty,"Prodi said at the signing ceremony.

Prodi's call was echoed by his successor Barroso.

"I hope that tomorrow the national parliaments and European voters will, in turn, shoulder their responsibility and approve this Constitution," the incoming chief of the EU executive said.

To make sure the smooth ratification of the bloc's first ever Constitution, European Parliament President Josep Borrell urged more work to do by the EU member states.

The ratification "lies with the people, who will be called upon to ratify the Treaty through their parliaments or via referenda." "Let us do what is necessary to win the trust of our citizens," he stressed.

The EU Constitution treaty was finalized on June 18 of this year at the EU summit in Brussels after years of bargaining, including a failing record in last December's EU summit in Brussels.

After Friday's signing, the treaty still needs ratification by all EU member states, whether through parliamentary balloting or referendum, before it could enter into force.

The treaty itself promulgates that it "shall enter into force on November 1, 2006, providing that all the instruments of ratification have been deposited."

If the treaty is not ratified before November 1, 2006, it shall enter into force "on the first day of the second month following the deposit of the instruments of ratification by the last signatory State to take this step."