The North's Deputy First Minister, Mr Seamus Mallon, has taken a major initiative to break the logjam on decommissioning, which is threatening to undermine the peace process.
The move signalled an intensification of the efforts to resolve the crisis. However, initial unionist reaction was negative.
Addressing the opening night of the SDLP conference in Newry, Co Down, last night, Mr Mallon sought to allay unionist fears on paramilitary weapons.
He pledged the SDLP would support the exclusion of Sinn Fein ministers from government in the North if the party failed to meet its decommissioning obligations.
Acknowledging unionist fears that Sinn Fein would "pocket" concessions, such as the release of prisoners, but fail to honour the agreement's terms on decommissioning within the specified two-year period, Mr Mallon said:
"I believe that this will not occur, and that it is not intended. But no one should have any doubt that if it did happen the SDLP would rigorously enforce the terms of the agreement and remove from office those who had so blatantly dishonoured their obligations."
This key passage in his speech appeared under the heading "Solemn Guarantees from the SDLP". Mr Mallon also promised Sinn Fein he would oppose any attempt by unionists to set new demands and conditions to exclude them from executive office.
Under the Mallon proposal, the Ulster Unionist Party would agree to Sinn Fein membership of an executive on the basis of an SDLP undertaking to expel the republicans if they broke the terms of the agreement on decommissioning.
There are varying interpretations of the decommissioning provisions in the agreement. Unionists say the pact requires IRA decommissioning before Sinn Fein can take cabinet seats; Sinn Fein says the document only obliges parties to use "any influence they may have" to achieve decommissioning.
Mr Mallon said that, contrary to the impression conveyed by some unionists, there was no paragraph in the agreement which made decommissioning a condition for Sinn Fein membership of an executive. He added: "To listen to some Sinn Fein spokesmen you would believe there was no paragraph on decommissioning at all. There is."
Initial reaction from unionists to the Mallon proposal was negative.
Senior UUP sources said: "Seamus seems to be telling a story of the next two years which ends happily ever after, but it lacks the key opening line: `Once upon a time the unionists sat down with Sinn Fein in an executive before decommissioning'. Seamus's plan is purely academic because the situation is not going to arise." Sinn Fein sources said: "Seamus Mallon is quite correct that there is absolutely nothing in the agreement stating that decommissioning must commence prior to the formation of an executive. Sinn Fein has been acknowledged by the governments in Dublin and London and by Mr Mallon's party leader, John Hume, as carrying out its commitments regarding decommissioning as laid down in the Good Friday agreement.
"Bertie Ahern and John Hume have also acknowledged we went further than the agreement requires by appointing Martin McGuinness as Sinn Fein's representative to the decommissioning body."
Meanwhile, the British government is believed to be preparing a fresh effort to try to establish the institutional structures of the agreement before Christmas.
Expectations of an urgent London initiative grew last night as it emerged that ministers and officials appear to be rejecting suggestions that the issue of decommissioning paramilitary weapons can be "parked" until next spring.
That option - canvassed in the last fortnight by the Taoiseach, Mr Ahern - was being effectively closed off last night.