There is an American phrase, "thinking outside the box", that is frequently mentioned in the context of the peace process. It first occurred in Conor O'Clery's book, The Greening of the White House, where two Irish-Americans used it in a discussion on how to rectify what seemed at the time like an intractable problem.

The history of the peace process sometimes seems like a series of brick walls which were somehow scaled or broken through or dismantled or got around because the will to move forward was always there, shared by a diverse community, from republican revolutionaries looking for a way out of violence to unionists prepared to give a little to save a lot.

On each occasion the problem or brick wall seemed insurmountable and no solution was in sight. We have arrived today at another of those stages. The immediate result of last night's IRA statement will be to render this afternoon's meeting of the Taoiseach and the British prime minister a fairly hollow affair. That will not matter much if, in the longer term, a resolution of the impasse can be found, although at this stage Mr Ahern and Mr Blair must be scratching their heads.

The Taoiseach will have reason to feel sore about being made to look foolish while he was on his feet in the Dail. His predecessor as Fianna Fail leader, Albert Reynolds, may permit himself a wry smile as he recalls a previous occasion when, as Taoiseach of the day, he was left in the dark in Leinster House due to Mr Ahern's failure to pass on a piece of paper containing crucial information.

But even Mr Ahern's embarrassment, though unnecessary and unhelpful, will not matter greatly if in the longer term a weapons formula can be found which assuages unionist fears without wounding republican pride.

Like the second shoe waiting to drop in the hotel room above you, the IRA statement came as no surprise, although it was still a bit of a jolt. It was certainly a major setback, since it was probably the first time in 200 years of republican history that the movement was discussing the issue of voluntary disarmament with an official body.

The question that presumably will exercise the minds of the two leaders in London this afternoon is whether the offer the IRA put on the table to Gen. de Chastelain can be restored and clarified - or if it has gone for good. Indications last night were contradictory and not always encouraging.

Long-time Provo-watchers thought the debate on decommissioning would have to shift to new ground. The faction within the republican movement which favoured a straightforward and blunt refusal to discuss the issue had won out over the "fancy footwork but still no hand-over" wing. These observers believed there would be no more talk of decommissioning or even putting weapons beyond use from the IRA. The approach of at least agreeing to discuss the issue and trying to advance the peace process through "constructive ambiguity" had become devalued currency, because the unionists and the British government were seen by republicans to be acting in bad faith.

Sources with an insight into the IRA's internal life said the whole decommissioning debate had caused considerable turmoil, with Sinn Fein leaders Gerry Adams and Martin McGuinness put to the pin of their collars to calm and reassure the paramilitary wing.

An alternative analysis of the current impasse held out greater hope. The IRA move was tactical and some creative "thinking outside the box" could move the situation forward. But first it was necessary to return to the text of the Belfast Agreement which did not mention Sinn Fein or the IRA but bound all parties to use any influence they possessed for the purpose of achieving total decommissioning.

On a recent visit to Belfast, the South African politician and peace negotiator Roelf Meyer urged all the parties to appoint representatives to the de Chastelain commission. Were the unionists and SDLP, for example, to take such an initiative, it might restore the position of those republican leaders who have taken the view that engagement and dialogue on weapons is better than the "stone face".

Senior political sources were still hopeful that the IRA was playing a tactical game rather than taking an irrevocable step on the weapons issue: "It's quite a calculated upping of the ante."

What can the two governments do? Encouraging the other parties to draw the implications of what they signed up to in regard to decommissioning, without prejudice to their views on the republican role, might be a start. Mr Mandelson, who impressed nationalists with his firm stance in principle on the Patten report, needs to mend some fences with the republican side. This astute politician will not want his report, at the end of his Northern Ireland stint, to be: "Honey I lost the ceasefire". It appears his meeting with republicans yesterday was as bad as it gets, but accounts differ as to who patronised whom.

As the problem is currently perceived, there seems to be no escape from the iron logic of "No David Trimble, no peace process". No nationalist or republican wants Peter Robinson, say, as first minister. But it is time to move the process on to new ground, for unionists to show they are still listening and sincerely want to restore the executive, and not engaged in some nefarious plot to undermine the Belfast Agreement or pursuing the highly unrealistic aim of governing with the exclusive support of the SDLP.

In that sense, despite all the thundering and the outrage, the ball is at the unionists' feet.