The European Union needs to remain open to further enlargement in line with its commitments, its responsibilities and its principles, but future enlargements will pose "very serious challenges", the Taoiseach has said.
Addressing a reception for EU Heads of Mission in Dublin this evening ahead of the European Council next week, Mr Ahern said Ireland had "traditionally been a firm supporter of enlargement".
"After all, we were one of the first beneficiaries of this process when we joined in 1973," he said.
"There are, it has to be acknowledged, very real concerns about the Union's ability to increase its membership substantially in the years ahead. But the debate should not be about placing new obstacles in the way of the candidate countries, or those in the Western Balkans who have already been given a membership perspective. It is an unavoidable reality, however, that future enlargements will pose very serious economic, political and institutional challenges for the Union."
Mr Ahern warned that attention needed to be paid to the public mood with regard to enlargement.
"Taking on additional commitments at this time would only add to public uncertainty. After next month, there will be a natural pause in the enlargement process.
"The EU needs to avail of this opportunity to get its future strategy right."
Mr Ahern noted that unfortunately, negotiations with Turkey on its application to join the EU had become deadlocked.
"This is because Turkey has yet to implement the Ankara Protocol and needs to do so sooner rather than later if its negotiations are to make satisfactory progress. We all have a shared interest in keeping these negotiations on track, but we need real cooperation and movement from Turkey," he said.
He commended the current Finnish presidency for its "unstinting efforts" to resolve the impasse.
Mr Ahern said the Union had successfully enlarged its membership on five previous occasions and that it could do so again in the future.
"After Bulgaria and Romania join on 1 January next, the Union will have no pressing enlargement decisions to take for some time. It is important that we make a success of the enlarged Union of 27 member states as this is the best way in which we can demonstrate the Union's capacity to expand further its membership during the next decade and beyond."
The Taoiseach also noted the European Commission's "sound proposals" for dealing early with difficult issues in relation to accession, including judicial reform, administrative capacity, the fight against corruption and organised crime.
He said the enforcement of "rigorous but fair" conditions would be essential.
"This approach should improve the quality of the accession process and reassure the public that these issues are given the priority they deserve."
On illegal immigration, the Taoiseach said events had made clear "again and again" that this was a "serious challenge for all of us".
"It is one to which the Union must respond with the full range of policy instruments at its disposal," Mr Ahern said.
