Up to 5,000 people are expected to attend Fianna Fáil's one-day ardfheis in Killarney tomorrow, the first time the party has held such a gathering outside Dublin.
In a message to delegates in the ardfheis programme, the Taoiseach has stuck a note of "optimism tempered by common sense".
Mr Ahern said: "The changed international circumstances in which we now find ourselves mean that we no longer enjoy all of the options that we did even in the recent past."
Acknowledging the "unease" and "new concern about the future" shared by voters, he said the economy was still doing "extraordinarily well".
"If we have the political courage to do what is right, then we can look forward with confidence to a bright future. The world-beating formula of the last decade is still working," he declared.
"Ireland today is a country of high expectations. That is a good thing. It is a consequence of success. However, continuing success can only be built upon reality and common sense."
Unusually, the ardfheis is being confined to a single day, though delegates will break off to view the key Ireland/Switzerland Euro 2004 qualifier.
Titled "Working, Building, Leading", the conference agenda will deal with "challenging times", and the need to offer both better public services and better value to taxpayers.
Furthermore, no motions are being taken from delegates, though senior Fianna Fáil figures denied suggestions they are trying to stifle debate.
A full-scale ardfheis will be held next March to launch the party's local and European Parliament elections campaign.
Newly-appointed general secretary, Mr Seán Dorgan, rejected charges that the party's grassroots are in rebellious mood.
"While there are undoubtedly concerns, people are looking for reassurance and information."
