Decommissioning is the millennium bug of the peace process. It has the potential to bring the elaborate governmental structure agreed at Castle Buildings last Good Friday crashing around our ears.

Senior figures in both governments have been saying for some time that they "haven't a clue" how to get around the latest and most threatening manifestation of the decommissioning virus. Various ideas have been test-marketed with both the unionists and Sinn Fein, but nothing has caught the imagination of either side.

"There are no breakthroughs. Don't kid yourself," one peace process insider said. Yesterday saw a round-table meeting of the parties with the First and Deputy First Ministers at Stormont, but decommissioning wasn't discussed. The issues concerned arrangements for getting the North-South ministerial council (NSMC), the British-Irish council and the civic forum off the ground.

These might seem somewhat abstract topics in the absence of agreement on decommissioning, but just because one piece of the jigsaw is missing doesn't prevent you from putting the other pieces in place.

If it ever takes place, the first meeting of the North-South council will be in Armagh. The inaugural of the British-Irish council awaits the establishment of the Scottish parliament and Welsh assembly, and the civic forum has yet to be dealt with.

Publicly and privately unionists and republicans remain as intransigent as ever on decommissioning. The most that can be expected from republicans, sources close to them said, is a statement from the IRA declaring its firm commitment to the peace process and reiterating its desire to see all the guns removed.

Sources said that while such a statement would be weighty in tone, content and historical import there would be no hand-over or destruction of weapons, nor would any explicit timetable for doing so be announced. But it would be the strongest hint so far that the IRA believed "the war", if not over, was certainly coming to an end.

But even a statement would not be forthcoming unless the republicans were sure that unionists would "buy" it. Republicans say they are not sure where the UUP's bottom line rests.

Senior unionists are bemused when told that republicans are unsure as to the UUP's true position on decommissioning. "They are not reading the newspapers or listening to what we are saying."

The UUP leadership would not countenance, and the party faithful would not allow it to accept, a statement, however weightily-worded, in lieu of hardware, unionists say.

Indeed, the UUP detects a shift in opinion, both public and official, in the Republic in favour of the unionist stance on weapons. Senior unionists claim the South is returning to the mindset of the mid-1920s and after, when the State set its face against private armies.

Certainly unionists have been courting Southern public opinion for some time as if they sensed, or even knew, that republicans see Dublin as the weakest element of the pan-nationalist consensus. A senior unionist recalled nostalgically yesterday how even Eamon de Valera had been forced to crack down very hard on the IRA because he felt it was jeopardising the safety of the State.

Wishful thinking, say sources close to official thinking in Dublin. Nevertheless, Dublin, London, the SDLP and just about everyone who wishes the process well are racking their brains to resolve the arms conundrum.

Meanwhile, Gen de Chastelain is still waiting in the wings. Like an actor in a rushed series of auditions, he can only say his piece once. If he fluffs his lines or if the script isn't up to scratch, a voice from the stalls will shout "Next!" Nevertheless, expectations remain high that the general can and will play a crucial role in overcoming current difficulties.

However, the only actual hardware the decommissioning body has received so far came from the Loyalist Volunteer Force. While there is widespread cynicism about that gesture, the point has been made that these are weapons which will never be used to kill anybody again.

While it is generally accepted that Sinn Fein has been punctilious in its dealings with the decommissioning body, the fact remains that no "product" has been forthcoming. Even a telephone-call to the commission indicating where arms might be found would be considered a valid gesture and a verifiable start to decommissioning, sources familiar with commission thinking said.

The appointment of Martin McGuinness as Sinn Fein's representative to the decommissioning body is seen as a highly-significant development because of his high standing among republican activists. There was considerable interest in remarks made recently by Mr McGuinness to the Belfast Tele- graph. He said that, had the power-sharing executive and the North-South council been established last year, "it is my view that we could have considerably advanced that [decommissioning] agenda".

Given that there is no indication - quite the contrary - that the IRA will decommission ahead of the planned transfer of powers to the Northern Ireland Assembly on March 10th, the spotlight has been turned on the various options open to Mr Trimble.

The scenario outlined by senior unionists last night was that the UUP leader would introduce a motion in the Assembly to block Sinn Fein participation in an executive because of the lack of decommissioning. That motion would probably fall for want of SDLP support and unionists would then ask London to invoke the agreement's review clause (Dublin's consent would not be required because this is a Strand One matter, concerning the internal governance of Northern Ireland, say unionists). In view of his past utterances on decommissioning, Tony Blair would have to consent to a review, senior unionists said.

A different view, based on a very different interpretation of the agreement, is that unionists could not prevent Sinn Fein participation in the executive and if they tried to do so republicans would be entitled to take a court action. This is a course of action Sinn Fein will be loath to take unless absolutely necessary, because of its traditionally suspicious attitude to the United Kingdom judiciary.

Indeed, it may be a weakness in the Good Friday document that no provision is made for a neutral body to adjudicate on different interpretations of the agreement, with the parties committed in advance to accept its decisions. The South has plenty of tribunals: why can't the North have one, too?