The British and Irish governments have confirmed that the formal review of the Belfast Agreement will begin in Belfast on Tuesday, February 3rd.
The Taoiseach, Mr Ahern, has said it should be completed by Easter, while acknowledging this may prove "a line in the sand".
He was speaking outside 10 Downing Street yesterday after a working lunch with the British Prime Minister, Mr Tony Blair, during which the two discussed the review and the Irish presidency of the European Council.
It is understood Mr Blair and Mr Ahern were dining when the news arrived from Belfast that the DUP leader, the Rev Ian Paisley, is standing down from the European Parliament in June.
Irish and British officials refused to be drawn on the reaction of the two leaders to a development which is bound to fuel speculation about Dr Paisley's eventual retirement from front-line politics, his likely successor, and its impact on the long-term prospects for a political accommodation in the North.
Mr Ahern was sticking yesterday to the position of both governments that the Belfast Agreement is not up for renegotiation.
He said the purpose of the review was "to find a way forward, obviously, to try and see if we can get the institutions set up on the other side of the review, and to get a stable Executive and the Assembly working again."
Mr Ahern also confirmed he hoped to fix a date and location for his first meeting with Dr Paisley's DUP within the next few weeks. It is expected the meeting will be held in London.
Mr Ahern indicated that the review should sit twice a week, and that meetings should be round-table rather than bilateral.
Twice weekly sessions would be necessary to maintain "tension and momentum" in the process, Mr Ahern said. No one had suggested that the review could be concluded before Easter, while others had suggested more time might be needed. "But we're setting that line in the sand."
British officials insisted there was no tension between London and Dublin over Mr Ahern's apparent willingness to allow the review to go beyond Easter.