Ten new countries join the European Union today. This marks an unprecedented historic event, with the largest single enlargement the Union has ever seen uniting 25 sovereign states in peaceful integration.
It once again confirms the original raison d'etre of the European Community. It was set up with the bold and ambitious vision in the wake of World War II to ensure that such an atrocity would never happen again and to ensure that the citizens of Europe would live together and build for prosperity in peace.
The enlarged Union will count 450 million people and will represent the biggest and most successful example of regional integration in the world. This is in itself very significant.
But most important of all is that the enlargement of the Union will strengthen the European Union as a Union governed by the rule of law, united in its diversity and fully committed to the principles of liberty, democracy and stability and to the ever closer union of peoples.
It is all too easy to take these very clear fundamental principles and objectives for granted as we become absorbed in debates on technical aspects of European Union membership but their importance could not be more obvious. The 10 new member states share these values and they belong to Europe.
Enlargement is also marked by unprecedented achievements on all sides. The states of central and eastern Europe have turned themselves into solid democracies and fully functioning market economies in a remarkably short period of time.
Driven by the prospect of membership, they have undertaken radical and fundamental reforms at all levels with a vigour that can only deserve the admiration of all.
In comparison to previous enlargements, the challenges have been considerable.
In the years since the first enlargement in 1973, sovereignty and competences have been pooled on a much wider range of policies.
The EU now offers a wide-ranging single market, an economic and monetary union with the euro as a common currency, the Schengen area, providing citizens with more internal freedom of movement, cooperation in the field of justice and a common foreign and security policy.
Meeting the requirements of EU membership today is tough, requiring considerable efforts at all levels and has only been achieved by the new member states with the tenacious commitment, leadership and conviction of all involved.
It is also a credit to the European Union's pre-accession strategy that the seemingly unattainable goal of reuniting the European continent has been achieved in such a short period of time.
Launched in 1993, the pre-accession strategy was addressed to the needs of each of the candidates, offering for the first time in a single framework considerable financial assistance in support of the preparations for membership.
The European Union's commitment to make enlargement a success was also demonstrated time and again throughout the accession negotiations by its determination not to dilute the whole range of principles, policies, laws, practices and obligations that constitute our patrimony, the so-called acquis communautaire, while at the same time safeguarding the effective functioning of the enlarged Union.
The thoroughness and intensity of the accession negotiations resulted in a comprehensive and balanced outcome, which now provides a solid basis for the smooth integration of the new member states.
Given the volume and scope of the acquis, the transitional arrangements agreed to enable the new member states to cope successfully with the obligations of membership are surprisingly few in number and clearly limited to the first few years of membership.
Moreover, the invaluable process of monitoring each of the new member states' preparations for accession right up to the eve of membership has contributed decisively to creating a climate of confidence between the new and the existing member states.
The European Commission indicated recently that it had not identified any area where safeguard measures would be needed as of May 1, thus dispelling earlier fears about the state of preparedness of the new member states.
Clearly, in terms of economic and social development, the new member states still have some catching up to do. Membership will be a catalyst in this regard both for generating prosperity and for increasing solidarity among the member states.
The new member states will benefit from EU structural assistance. But accession is more than just about money; the progress achieved by my own country, Spain, during almost 20 years of membership, demonstrates how accession can bring about positive political, democratic, social and economic change. I have no reason to believe it will be otherwise for the 10 new member states.
The Union is, of course, not a stranger to change itself and it can be said that it thrives on its own dynamic of progress and forward movement.
In this respect, the 10 new member states join the Union at an important moment. It is hoped that the discussions on the draft constitution for Europe can be successfully completed in June 2004. This will mark an important turning point for the Union. I am confident that there will be the necessary political will, responsibility and determination to act in the best interests of the European Union and in the future of Europe.
However, constitutional treaties need time and ratification is a lengthy process. The EU of 25 will therefore function on the basis of the existing treaties for the foreseeable future. On a practical and functional level a lot has already been included in the Treaty of Nice to meet the challenges of enlargement providing for the institutions to operate effectively in an enlarged Union and for decision-making to be streamlined.
Furthermore, since the signing of the Accession Treaty in April 2003, the 10 new member states have been taking part at all levels of the work of the Council of the European Union and in the European parliament as active observers. This has been an invaluable learning experience for all involved.
With 10 more member states around the table and an increase in the number of official working languages from 11 to 20, there has also been a need to streamline the efficiency and conduct of meetings, as well as to address the question of interpretation and the translation of documents. Most of these measures are already in place.
Given its common objective to make Europe a continent of democracy, freedom, peace and prosperity, the Union is proving to be a very attractive club - and the enlargement train shows no sign of slowing down.
Bulgaria and Romania, which started negotiations in 2000, are part of an inclusive and irreversible process. Provided they are ready, it is our objective to welcome them into the Union in January 2007.
Both countries are strategically important for the European Union and for political and economic stability in the Balkans. The path to membership is not easy but I am confident that with the necessary political determination they will be able to meet the demands of EU membership on time.
The European Union will also be taking other important decisions in the near future; first at the European Council in June on whether to begin accession negotiations with Croatia, and later this December on the prospect of opening accession negotiations with Turkey.
The Council of the European Union will soon also examine the former Yugoslav Republic of Macedonia's recent application for membership.
In pursuit of its commitment not to tolerate any new dividing lines in Europe, the Union's European Neighbourhood Policy aims to promote stability and prosperity beyond the new borders of the Union both to the east and to the south.
Under this initiative, the European Union heads of state and government will be adopting a number of action plans in June this year in order to develop cooperation and encourage reforms in a number of countries.
This will deepen our existing bilateral relations to the mutual benefit of the Union and our neighbours, allowing them to participate progressively in major EU policies and programmes, including the EU single market.
So much has already been done and paradoxically we are now in a situation where May 1 could be an anti-climax. The new member states are well prepared, with many aspects of membership already a reality at home.
In Brussels, the Union of 25 is in full force to face the challenges ahead. The Union is changing, for the better. We are counting on our new Union members when the big decisions need to be taken.
Their arrival serves as a constant reminder of what the Union is all about, diversity in unity.
Javier Solana is the EU's High Representative for Common Foreign and Security Policy.