The Taoiseach will meet the British Prime Minister in Downing Street tonight to set the agenda for the next week of talks designed to save the Belfast Agreement.
The pro-agreement parties and the two governments have six weeks to reach a deal to prevent a serious political crisis in the North.
Mr Ahern and Mr Blair will seek to narrow down the areas of disagreement with a view to focusing the series of talks, due to start in Belfast tomorrow or Friday, on the remaining differences.
They are expected to consider proposals for further police reform measures sought by nationalists, as well as demilitarisation moves which could be taken by the British government as part of a deal.
Mr Ahern will join Mr Blair for a working dinner to discuss plans for crucial negotiations due to start next week.
The Northern Secretary, Dr John Reid, and the Minister for Foreign Affairs, Mr Cowen, are due to chair talks with the political parties in the North tomorrow or Friday. Mr Ahern and Mr Blair are expected to travel to Belfast to join the negotiations next week.
A Downing Street spokesman said that at tonight's meeting the two men would "review the state of the process" following Mr David Trimble's resignation as First Minister last weekend.
Failure to reach a deal over the next six weeks could result in either the suspension of the North's political institutions or fresh Assembly elections.
Asked if either option was under consideration, the Downing Street spokesman said: "We should concentrate on the progress we can make this week and the next and see where we go from there rather than constantly jumping one step ahead of another. We need to see how far we can go in terms of pushing the process forward over the next few weeks."
The spokesman said there would be an "intensification" of negotiations over the next fortnight. He insisted there were no deadlines for progress. "The problem is not one of time. The problem is of making progress together on the issues," he said.
Focusing exclusively on decommissioning would damage the peace process. It was only one of several issues which needed to be addressed. "Experience suggests that if you isolate one element, you are not going to make the progress you need across the board," he said.
Meanwhile, the SDLP Minister of Agriculture, Ms Brid Rodgers, has called for movement on decommissioning by the Provisional IRA, saying it would build confidence in the Belfast Agreement among unionists.
"Republicans have sought and have been granted confidence-building measures through out the process. Therefore, they more than anyone must understand and respect the need for such measures and provide the pro-agreement unionist community with similar confidence-building steps," she said.
"Their repeated commitment to initiate a process of decommissioning and their repeated failure to do so has clearly sapped the confidence of pro-agreement unionists. The political process, which republicans claim to support, cannot and will not survive unless the need for confidence-building within both communities is recognised or acted upon.
"The failure to decommission is the largest obstacle to progress at this present time. It must be addressed with great urgency in order to allow the process and the community to move on."