If the row which brought an end to the Brussels summit isn't resolved soon, the European Union could be in a mess for two years, arguing over money and power, writes Denis Staunton.
The collapse of this weekend's talks on a constitutional treaty presents the European Union with a serious dilemma and creates a formidable challenge for the Irish EU presidency during the first half of next year.
The summit's failure puts in doubt the future of the constitutional treaty, which has been two years in the making and was designed to make an enlarged EU more democratic, more efficient and more transparent.
It has prompted renewed calls for a "two-speed Europe" in which a core group of countries would press ahead with deeper integration, leaving the rest to catch up later, if at all.
The French President, Mr Jacques Chirac, and the German Chancellor, Mr Gerhard Schröder, said on Saturday that they would now look at ways of co-operating more closely on a range of issues and Paris and Berlin are today expected to announce an initiative to work more closely on some justice and policing matters.
The Brussels summit failed because EU member-states were unable to agree on a reform of the voting system in the Council of Ministers, where national governments decide on EU legislation.
France and Germany wanted to replace the system of weighted votes agreed at Nice with a "double majority" system reflecting population size. Under the new system, a qualified majority would be defined as a majority of member-states representing at least 60 per cent of the EU's population.
Spain and Poland, which enjoy almost as many votes as the EU's four biggest states under the Nice system, were resisting any change which could diminish their influence.
The disagreement should not mask the fact that the EU's 25 present and future member-states agree on almost everything else in the constitutional treaty, although a handful of issues, including a proposal to abolish the national veto on some tax questions, remain to be resolved.
The Taoiseach said on Saturday that there was no sense of abandonment of the treaty-making process and the Irish presidency will deliver a report on the prospects for progress at an EU summit in March.
Officials say that Mr Ahern is determined to "have a go" at finding agreement but he cannot yet estimate his chances of success.
A number of other EU leaders have written off the possibility of finding agreement during the next six months and the Dutch Prime Minister, Mr Jan-Peter Balkenende, is preparing to take over negotiations during his country's presidency in the second half of 2004.
Some senior EU diplomats predicted yesterday that the disruptive effect of Spanish elections in March and European Parliament elections in June mean that the treaty is unlikely to be approved until 2005.
As the months pass, the chance will become greater that the constitutional talks will become entangled in negotiations over the EU's financial perspectives - a seven-year budget which determines how much each country pays into the EU and how much each receives in structural and other funds.
The budget negotiations will not be completed until 2006 but they will start early next year when the European Commission presents its proposals. Germany has hinted that Spain and Poland could be punished for their stance on the constitutional treaty by receiving lower subsidies from the EU in future.
If the Irish presidency succeeds in finding agreement on the treaty, it could save the EU from two years of unnecessarily bitter and divisive disagreement over money and power. After this weekend's debacle in Brussels, however, it could take time as well as negotiating skills to create an atmosphere capable of producing agreement.
As the President of the European Parliament, Mr Pat Cox, put it on Saturday: "You don't go from today's hospital ward to tomorrow's Olympic Games. You have to go through some kind of physiotherapy."
Mr Chirac and Mr Schröder, at least, will not be hanging about to see how effective such diplomatic physiotherapy proves to be. Following the collapse of the talks on Saturday, they both expressed a renewed interest in a "two-speed Europe" and Mr Chirac referred to a speech he made to the German Bundestag in 2000.
In that speech, in which the idea of a convention to draw up a European constitution was first mooted, Mr Chirac said that "the capacity for forward momentum" must be preserved in an enlarged EU.
"There must constantly be the possibility of opening up new avenues. For this and as we have done in the past, the countries which want to integrate further, on a voluntary basis and on specific projects, must be able to do so without being held up by those who, and it is their right, don't wish to go so fast," he said.
Mr Chirac stressed on Saturday that such integration should take place on the basis of "enhanced co- operation" rules agreed at Amsterdam in 1997 and revised at Nice in 2000 and that the "pioneer groups" should be open to all member-states that wish to join.
French and German officials point out that not all EU countries have adopted the euro or have removed border controls under the Schengen agreement and that differentiation has always been a feature of the EU. Critics fear that such pioneers could become the basis of a two-class as well as a two-speed Europe, with an inner core of prosperous member-states, mostly in western Europe.
Regardless of its merits, the proposal for a two-speed Europe can only make the Taoiseach's task more difficult as he seeks to resolve remaining differences over the constitutional treaty.
After almost 20 years attending EU summits and following his experience with the Belfast Agreement, Mr Ahern is among the most experienced political negotiators in Europe.
During the next six months, his political judgment and negotiating skills will face their toughest European test yet.