The Taoiseach has challenged would be opponents of the Lisbon Treaty to list the benefits to Ireland of voting No in the upcoming referendum.
Mr Ahern told the National Forum on Europe in Dublin Castle: "I believe saying no is not enough, they [opponents to the treaty] must spell out the benefits that they see accruing to Ireland in saying no."
In his first major public statement on the treaty Mr Ahern said he is convinced that when Irish people reflect on the issues raised, they will be "sensible and pragmatic" and want "full Irish engagement in a Europe that will be improved and reinvigorated".
The Taoiseach said: "The Irish people want a Europe that is equipped to support social and economic development and job creation, and rise to the global challenges of the 21st century."
"I also believe strongly that Ireland is now presented with an opportunity to affirm our commitment to the European project in these times of global economic turbulence," he added.
Cautioning against taking the Union for granted, the Taoiseach recalled the benefits to Ireland of EU membership ranging from the single market and the euro, to cheaper air travel, the European Health Insurance Card scheme and the freedom to travel, study and work across Europe.
Concluding his address, the Taoiseach said that Ireland was presented with an opportunity to affirm its commitment to the European project in "these times of global economic turbulence".
"That message of support will send a positive signal of Ireland's ability and willingness to embrace change and maintain a leadership role in the new global economy," he said.
The Government has yet to make a decision on when to hold the vote, however, Mr Ahern today hinted that it could take place before the summer. A formal announcement is expected within weeks.
The forum is holding a series of public meetings around the country featuring speakers both for and against the treaty. The Government is to send out 2.5 million information booklets on the treaty in coming weeks.
According to the latest Irish Times/TNS mrbi poll, nearly two-thirds of the electorate don't know how they will vote in the forthcoming referendum.
