The Prime Minister and the Taoiseach, who failed to end the impasse over arms decommissioning, agreed to hold the fresh talks after their second meeting in 24 hours last night at No 10.
There was also a hint that the governments are prepared to alter the wording of the Hillsborough Declaration when they meet party leaders on Monday. Mo Mowlam, Secretary of State for Northern Ireland, will hold more talks with other party leaders in Belfast.
Conceding that there were "difficulties" in reaching agreement, the Prime Minister's spokesman said the declaration was a draft document, in a clear signal that it could be changed. He remained confident the obstacles could be overcome, providing the momentum was maintained in the peace process.
After an hour-long meeting with Mr Blair, Mr Ahern said: "It is clear to us that the Hillsborough Declaration has not yet got the widespread support that we would like. As a result, it is clear to us we have not yet reached a form that will give us a consensus that the Good Friday Agreement had. We will have to continue to do that, regardless how difficult that is."
Ms Mowlam said: "There is a determination that no one wants to stop."
Mr Ahern said both governments were committed to achieving implementation of the Good Friday Agreement with the establishment of a new power-sharing executive for Northern Ireland.
Earlier, the Sinn Fein chairman, Mitchel McLaughlin, said the credibility of the Good Friday Agreement had been "seriously eroded" and warned the two governments against "parking" the peace process over the summer months.
David Trimble, the First Minister of Northern Ireland, said that would not happen. However, he said it was now up to Republican leaders to confront the hardliners within their own ranks who, he said, were barring any moves towards decommissioning.
"It is time that the leaders of the republican movement stood up to the handful of paramilitaries in their ranks that are obstructing progress," he said. "It is time they faced down the opposition in their own ranks."