The Taoiseach, Mr Ahern, said today Ireland would use its presidency of the European Union to try to make progress on the stalled European Constitution - but warned that it could take "some time" to resolve the outstanding issues.
Mr Ahern struck a cautious note about the prospects for reviving the constitution - which EU leaders failed to agree in Brussels last month - during Ireland's six-month presidency, which starts today.
And he cautioned against bigger countries such as France and Germany trying to progress at a faster rate than the rest of the expanding EU - the so-called two-speed European scenario.
Mr Ahern told BBC Radio 4's Todayprogramme: "After the breakdown it is a time for reflection.
"Our tactic will be to take where the Italian's finished off, to try to take their draft treaty, and try and first of all to make sure that the issues involving compromises, that they will hold, and then start testing the ground with the other countries to see how much progress we can make.
"It is quite a long task and I think that is the inevitability of the process. It is a very fundamental change."
But Mr Ahern said he believed the constitution would be achieved in due course.
He said: "I am confident that we will have a constitution. I am confident that the perimeters of that will be around where we were in the last 10 weeks but I think there are still very fundamental issues that have to be worked out.
"Weighting of votes is one thing, justice and home affairs is another, taxation policy, whether it is unanimity or otherwise, these are all large questions.
"Then there are the big countries that believe that perhaps if small countries are not ready, then they should move ahead, back to the two-speed Europe. There are many things that have to be sorted out and it is going to take some time to do that."
Mr Ahern said that he thought that a two-speed Europe would be a divisive development, because the smaller countries would struggle to catch up with those on the fast track.
He said: "It would create many disparities and divergences that certainly would not be good for the overall European population."
PA