The IRA is set to reject pressure from the Irish and British governments to reveal further details of the weapons it put beyond use last Tuesday.
The Government adopted a deeply pessimistic tone last night, with the Taoiseach, Mr Ahern, expressing doubts over whether the North's power-sharing Executive could be re-established by Christmas.
Intensive contacts over the last two days between the governments, republicans and the decommissioning body are understood to have come close to ending hope that the IRA will agree to have further details released, as required by the Ulster Unionist leader, Mr David Trimble.
"I think Sinn Féin will say we can do no more," the Taoiseach said on The Dunphy Show on TV3 last night. "I think the IRA will be reluctant to do any more."
Mr Ahern's comments came after the British and Irish governments are understood to have heard that there appears to be no prospect of an IRA agreement to publish more details of last Tuesday's act of IRA decommissioning, overseen by GenJohn de Chastelain.
The news of the IRA's attitude follows reports that Ulster Unionists were about to seek not only details of the decommissioning act that took place last Tuesday, but also a timescale for the completion of the decommissioning process.
With the Ulster Unionist executive due to meet in Belfast this morning, there were indications the party's attitude might harden still further. Yesterday Mr Trimble, insisted that he will not share power with Sinn Féin in a restored Executive unless the IRA offers more information about last week's weapons decommissioning.
Mr Trimble downplayed hopes that a resolution to the latest crisis could be found before the Assembly elections, which he is now almost certain to fight in the absence of any political deal over what happens afterwards.
Asked if a solution could be found before a further meeting of the UUP's Executive Council on Wednesday, he said: "There doesn't appear to be. Whether that will still happen I don't know. It rests with other people.
Meanwhile, the international decommissioning body has declined to back assertions by the Taoiseach and the British Prime Minister, Mr Blair, that it gave them significant extra information last Tuesday on the IRA act of decommissioning, which had not been made public.
As Mr Blair faced Conservative and DUP allegations yesterday of misleading the House of Commons, a spokesman for Gen de Chastelain refused to confirm or deny the two leaders' statements. The spokesman told The Irish Times last night that the general, accompanied by his colleague, Mr Andrew Sens, did not hand over any inventory of IRA weapons when he met the two leaders at Hillsborough last Tuesday. "We cannot go beyond that," the spokesman added.
The DUP claimed yesterday - and the decommissioning body did not deny - that the general told them he gave the leaders no extra information.
On Wednesday, Mr Ahern gave the clear impression that he was in possession of significant extra information. He said he and Mr Blair had considered the argument that the governments should "publish what they know".
In the Commons last Wednesday, Mr Blair said they had been given "certain information" on the matter and that "although we are not at liberty to disclose that information ... we are working hard to try to find a way in which we can do so."