European Diary: The next three days could be crucial in determining the fate of the EU's constitutional treaty as the Taoiseach completes his tour of European capitals with visits to Paris, London and Berlin.
Irish presidency officials are confident that all remaining disputed issues in the treaty can be resolved at this month's summit in Brussels, but a deal could yet be wrecked by even one country that lacks the political will or capacity to make the necessary compromises.
Mr Ahern's tour this week, which will also take him to The Hague, Brussels, Luxembourg and Copenhagen, will also give him a final opportunity before the summit to test opinion among EU leaders on who should succeed Mr Romano Prodi as President of the European Commission. Two Prime Ministers have emerged as front-runners: Belgium's Mr Guy Verhofstadt and Austria's Mr Wolfgang Schuessel.
One EU leader said this week that Mr Verhofstadt enjoyed the support of a majority of member-states, but Irish officials insisted yesterday that the race remained open.
An enthusiastic European integrationist, Mr Verhofstadt has been perceived as the favoured candidate of France and Germany, with Britain leading the opposition to him.
Reports from Paris this week, however, suggest that the French government may be cooling towards the Belgian liberal, while London's opposition remains as firm as ever.
Mr Schuessel enjoys the support of many small member-states, particularly among countries in central and eastern Europe referred to by one EU official as "the Austro-Hungarian empire".
The Austrian might also be acceptable to Germany, not least because his mother tongue is German, but Berlin is unlikely to back any candidate without French support.
Mr Schuessel faced a six-month boycott from other EU leaders when he entered government with Dr Joerg Haider's far-right Freedom Party, with which he continues to share power. The French President, Mr Jacques Chirac, is unlikely to support the Austrian Prime Minister for the Commission job, although presidency officials say that Mr Chirac has been more conciliatory on the issue than they expected.
If neither Mr Verhofstadt nor Mr Schuessel command enough support, the smart money is on Denmark's Mr Anders Fogh Rasmussen.
A liberal, Mr Rasmussen ran a very successful EU presidency two years ago, although he upset some EU leaders by authorising a fly-on-the-wall television documentary that portrayed them in an unflattering light.
The choice of Mr Prodi's successor is expected to be made after the treaty negotiations are over unless a clear favourite emerges this week.
There are four main unresolved issues in the treaty: the system of voting in the Council of Ministers; the size and composition of the Commission; the extension of qualified majority voting to new policy areas; and the minimum number of MEPs to be sent from each member-state.
All governments now agree that the system of weighted votes in the Council of Ministers should be replaced by a "double majority" system reflecting population size. A final deal is likely to include a mechanism to ensure that a small number of big countries cannot block any measure but that a substantial element - perhaps a fifth of member-states - can do so.
The Commission is likely to be limited to 17 or 18 members from 2014, and each country will probably be allowed to send at least five or six representatives to the European Parliament.
The presidency is confident that the arguments over extending qualified majority voting can be resolved without crossing any government's "red lines".
EU leaders agreed in March that they would make every effort to find agreement at this month's summit, and the presidency believes that all governments remain committed to securing a deal.
There is some anxiety, however, over the political situation in Poland, where the Prime Minister, Mr Marek Belka, lost a parliamentary confidence vote last month.
Presidency officials fear that, without the authority of a parliamentary mandate, Mr Belka could feel unable to budge from established Polish negotiating positions.
