The Fine Gael leader, Mr John Bruton, has warned that unless major progress is made by February at the Stormont talks, the process "could begin to unravel".
He told the Forum for Peace and Reconciliation there were about 18 working days left until the plenary session of the talks in February, and if there was little movement on the major issues "there could be serious problems".
He said there were major issues such as a North-South body with "executive" functions. Who would exercise budget authority over its spending, he asked. Would its work reduce the sense of isolation of nationalists in the North? The impact on their daily lives and not "economies of scale" should dictate its work.
He questioned the willingness of Departments and State agencies in Dublin to give up powers to the North-South body.
He said that if the North's internal institutions - a devolved assembly - did not work properly, then the North-South body would not work.
There were also issues around the Irish language and bilingual signs being allowed only in certain parts of the North.
Mr Bruton also stressed that while the talks were "understandably" taking place behind closed doors, it was also important to have a public debate so that when referendums eventually took place people would be fully informed.
In his contribution, the Taoiseach, Mr Ahern, said the Government was committed to "balanced" constitutional change as stipulated in the Joint Framework Documents.
"We have been re-examining how best to carry those commitments into effect, and we will be prepared to discuss these matters fully and openly in the negotiations."
He also referred to the controversial comments by the Minister for Foreign Affairs, Mr Andrews, in an interview, about the role of the North-South body. Some would describe what happened as a setback, Mr Ahern said.
Certain language used in that interview "went somewhat beyond what is the Irish Government's position on a North-South body but that was quickly corrected by the Minister himself. I am glad that the clarification was speedily accepted and that people did not dwell on it."
The SDLP delegation was headed by the party's deputy leader, Mr Seamus Mallon, who said that the talks process was the only option and all signposts had been leading in that direction since 1973.
He said there was "no other place to go. There is no other means to deliver a settlement."
The chairwoman of the Forum, Mrs Justice Catherine McGuinness, welcomed new delegates who included the Northern Ireland Women's Coalition, Labour in Northern Ireland and Senator Maurice Hayes. The British ambassador, Mrs Veronica Sutherland, and the US ambassador, Mrs Jean Kennedy Smith, also attended.
Mrs McGuinness told members the reconvened Forum would now sit every two to three months rather than every week as in the past. She said it was "clear to all" that the "process of negotiations has to be the primary arena and focus and the role of the Forum is now a supporting one of lending encouragement".
The Labour party leader, Mr Ruairi Quinn, said that for the first time in the peace process all the major players were meeting together. "For many, on all sides, it will require a leap of faith - a determination not to let the past dictate the future. It is a difficult job but we all know that the cost of failure is far too high."
The Alliance party leader, Lord Alderdice, reminded the Forum there were now fewer people represented in the Northern Ireland talks than there were in 1992, because, he said, the DUP "represents a very large proportion of the population".
The Tanaiste and Minister for Enterprise and Employment, Ms Harney, questioned the "ill-advised" absence of parties from the process.
