The Taoiseach insisted today IRA decommissioning must be complete and paramilitarism must be at an end before Fianna Fáil contemplates entering government with Sinn Féin.
However, Mr Ahern refused to speculate when this may be.
Questioned by reporters this morning about comments by Minister for Foreign Affairs, Mr Dermot Ahern, last week, the Taoiseach said: "When we get to completing the issue of decommissioning, when we see an end to paramilitarism, when we get a clear understanding...that we have one recognised army in this country, then we can feel that we have moved to a new stage."
Speaking after the annual Wolfe Tone commemoration in Bodenstown, Co Kildare, Mr Ahern added: "Until we get to that position, we can't speculate about it, and in the 40 or 50 times I've been asked this question, I will not speculate on it."
On Wednesday Fianna Fáil moved to distance itself from Mr Dermot Ahern's upbeat remarks about future Sinn Féin participation in government, saying the party had major steps to take before it can be seen as a coalition partner.
The Minister for Foreign Affairs said on Tuesday that it was "only a matter of time" before Sinn Féin was in government in the Republic. Speaking to reporters at Hillsborough he said Fianna Fáil's view that Sinn Féin should not be in government would change if circumstances changed. "I hope that happens in the future," he said.
Reacting directly to Mr Ahern's comments today, the Taoiseach said: "Dermot Ahern did an interview during the week. I didn't know he was doing the interview, I was away, and I the first thing I saw about Dermot Ahern's interview was your newspaper's headlines on it.
"The essential point in this is that our Constitution states there can be one Oglaigh na hEireann. At the moment there are two. So that's it, that answers the quesion. Dermot Ahern said that."
During his speech at the Wolfe Tone event, Mr Ahern said "no stone must be left unturned" to ensure the Belfast Agreement is fully implemented.
"Given the scale of our ambition and the opportunity that now exists to achieve it, there is a heavy burden on all of those within republicanism to bring this about," Mr Ahern said.
"A new Ireland based on the ambitions and ideals of the Good Friday Agreement is now an option within our grasp. History will judge harshly those who temporise and in so doing lose this historic opportunity."
