The Taoiseach has emphasised the Government's opposition to proposals to exclude Sinn Fein from a Northern Ireland executive if decommissioning does not take place.
Amid nationalist concern that such a move could be contemplated, Mr Ahern said yesterday that both the Belfast Agreement and last Friday's British-Irish plan to save it were based on "inclusion and not on exclusion".
The Belfast Agreement was "an exercise in inclusive, collective politics", he said. "That is the only way forward."
Mr Ahern's comments came the day after the British Prime Minister, Mr Tony Blair, indicated to the House of Commons that he might support moves to sustain a Northern Irish executive without Sinn Fein should the IRA fail to decommission weapons.
Mr Blair pointed out on Monday that according to the governments' plan if the IRA defaults on decommissioning, the institutions of the Belfast Agreement will be suspended.
But he added: "Suspension is not the only thing that happens. We go into review. Then we can invite the parties to take a different way forward."
However, he also indicated that he could not guarantee a new executive without Sinn Fein, saying that the SDLP, which would have to agree to any such move during a review, would have to speak for itself on the issue.
Mr Blair's statement was part of an intensive Downing Street effort to persuade the Ulster Unionist Party to accept the British-Irish document.
His suggestion that "a different way forward" could be found was seen by nationalists as an indication that he might support an executive being formed without Sinn Fein.
Unionists have demanded that Sinn Fein be excluded from an executive if decommissioning does not take place.
Simply suspending the institutions penalised all parties, according to Mr Trimble, and was "unfair".
However, the position of the Government, the SDLP and Sinn Fein is that Sinn Fein cannot be excluded from an executive under the terms of the Belfast Agreement. Mr Ahern said yesterday the inclusive nature of the exercise was crucial.
He praised the "real leadership" shown by Mr David Trimble, saying he hopes he will see the advantages for unionism in the British-Irish plan to save the Belfast Agreement.
He also said the debate on the formation of the executive and decommissioning must come to an end and that hard decisions must be made "to give effect to the will of the people".
After a meeting with a US congressional delegation in Dublin yesterday Mr Ahern said the plan drawn up by the two governments "offers a fair, balanced and honourable way forward for every body".
He said Sinn Fein's new position on decommissioning "was a deeply important one and should be acknowledged by all of us as a hugely positive and constructive contribution to the search for a compromise. And I know that it was a move not easily made."