The Irish and British governments will assess the state of the Belfast Agreement if the deadline of June 30th set by the British Prime Minister is not met, the Taoiseach told the House.
"If the parties to the Good Friday agreement have not made progress by June 30th, it would be for the two governments to reflect on that situation and see where we go from there," said Mr Ahern.
He was replying to the Labour leader, Mr Ruairi Quinn, who asked in what way collectively the Dail could assist him to ensure that the deadline was met and the outcome constructive and satisfactory.
The Taoiseach said that everybody in the House would continue to try to convince all of the Northern parties to make movement.
"It is very clear where the movement lies, and that all - it is not just one party - know what they have to do, some more than others. And I hope they can do that."
The Fine Gael leader, Mr John Bruton, asked if he was still of the opinion, expressed in February, that it was not practical politics to envisage the establishment of an executive without a start being made to decommissioning.
The Taoiseach replied that that was his position from a long way back. The current proposal relating to the June 30th deadline had "a lot of benefit," and he welcomed the "positive meeting" held earlier in the day by the UUP.
He believed that some of the spokespersons for the UUP, in their statements on Monday night, were misinterpreting some aspects of what happened last week.
"It was not a situation where people were asked to set aside the decommissioning issue. That was not what the outcome of those discussions were."
Mr Ahern said that the process was to be taken in two stages. Firstly, the d'Hondt system would be moved on Thursday, there would not be a formal meeting of the executive, and the ministers-designate would not take up their full positions until June 30th, or before that if that were possible.
Secondly, and separately, talks would continue and intensify between the chairperson of the international decommissioning body and the parties, with the decommissioning issue, or a means of trying to sort it out, very much on the agenda.
Mr Bruton asked if there was any indication that the IRA might be willing to make a statement about its medium-term intentions relating to decommissioning.
Mr Ahern said that a year ago one could not speak without using the term Sinn Fein-IRA, given that people took the view they were opposite sides of the same coin. Now people would say that Sinn Fein was not the IRA.
He added that he believed the Easter IRA statement contained many signals and phrases which were new and did not rule out a position on decommissioning at some future date. But he had no reason to believe that the IRA would issue a statement in the short term.