Leaders of the 15 EU member states ended their first day at the Nice summit having made little progress.

The headlines were made away from the conference hall as anti-capitalism protestors clashed with riot police after setting fire to a bank.

The bargaining for the crucial summit has variously been described as "complex" and "tough" and last week minister for Europe, Keith Vaz, predicted that the meeting could overrun into Sunday and see leaders having at least "two or three" sleepless nights.

The stakes are high, the conference is billed as one the most important in Europe's history since Yalta, and it could see the size of the union almost doubling to 27 states.

EU leaders met with the leaders from the 12 countries seeking admission to the union and stressed how much the candidate countries need to achieve before enlargement can begin in 2002. Countries such as Poland will use the conference to show how much progress they have made with the sometimes painful economic restructuring necessary for accession to the EU.

To achieve enlargement, however, the decision making structures of the union must be given a radical overhaul - which remains a contentious subject which is likely to divide those gathered in Nice.

The reweighting of votes in the EU's council of ministers is controversial in Germany, France, Spain, the Netherlands and Belgium. The French presidency is rejecting Germany's demands for an increase in its votes to reflect its large population. The disagreement means that a traditional Paris-Berlin axis can no longer be relied upon in the talks.

The extension of qualified majority voting is also a vexed question. The commission and the French presidency of the council of ministers, led by Jacques Chirac, want to scrap vetoes in 50 areas of the treaty - a move opposed by a large number of governments, including the French. The UK will support the end of vetoes in 17 areas but has drawn "red lines" around others - including the key areas of taxation, social security, border controls, defence and foreign policy.

The size of the commission will also come under scrutiny. Whilst all member states expect at least one commissioner, and sometimes two, the status quo would be unsustainable in an enlarged EU and member states must agree this weekend on how to reform the allocation of these key EU posts.