The scenario of an Ulster Unionist leader placing his future in the hands of the IRA is a plot twist worthy of Ripley's Believe it or Not. That is assuredly what David Trimble has done this weekend with his deadline for IRA decommissioning which, if not met, apparently triggers his resignation.

Instead of quietly shuffling the IRA off stage as the peace process was intended to do, the Trimble move has placed it at the very centre of the drama. It is doubtful if even the IRA members themselves wanted such a role at this moment.

They had, after all, just agreed to appoint an interlocutor, a huge step from their perspective, and an acknowledgment that decommissioning was an issue they had to deal with. That in itself took years to achieve.

Now they are being asked to jump through hoops and deliver product in double-quick time, merely to satisfy unionist concerns that they believe have as much to do with demanding surrender and fomenting splits as with furthering the peace process.

By demanding arms Trimble has signed a mutually-assured destruction pact with republicans. No decommissioning from the IRA by February means the end of his leadership. Without David Trimble, Sinn Fein leaders know, the end of the peace process that they worked so hard to create is inevitable.

It is a risky gamble by Trimble. No deadline in the life of the Belfast Agreement has been met to date, and this self-imposed one from Ulster Unionists is hardly calculated to impress the IRA.

They have shown themselves remarkably unimpressed when compulsion rather than persuasion is adopted as a political tool.

It is worth repeating that the key to achieving decommissioning is that it is a voluntary process, that there is no element of forced surrender or defeat attached to it, and that it is consistent with agreed progress in every other phase of the agreement. Any other scenario spells disaster.

For his own internal reasons, Trimble has now gambled on forcing decommissioning, an all-or-nothing bet, in return for sitting in government with Sinn Fein. Perhaps he had to do it, but he is now, surely, a hostage to IRA intentions.

He has upped the ante over an issue which security experts on both sides of the Border agree is purely symbolic rather than practical, as weapons can easily be replaced.

One can already hear the argument within the IRA army council that this is just another, more camouflaged, version of the unionist veto. There will also be suspicions of what one senior Sinn Fein source called "shabby dealing" by the British government with its side letters and secret assurances to leading unionists in the run-up to the vote.

Once again, republicans will feel that they are being squeezed, despite abiding by the letter of the agreement, to satisfy unionist insecurities.

There will also be a strong view that David Trimble was able to drag every other part of the process out until practically the eleventh hour, yet will now be indulged in attempting to force the decommissioning issue to a premature conclusion.

The date of May 2000 in the original Belfast Agreement was significant to republicans. It would undoubtedly have been the time for the seminal IRA review of the agreement, during which the primacy of politics and the outworking of the agreement would have been discussed in great detail.

Under the original plan envisaged in the Belfast Agreement, the executive and government and cross-Border institutions would have been set up by October 1998, and the IRA would have had the 20 months since then to evaluate the agreement, the policing report and the decommissioning issue.

Because of the foot-dragging that sees the institutions being set up only this week, 18 months late, and now the unionist ultimatum on guns, that IRA review will be telescoped into a period of a mere two months, part of which will be lost to the Christmas season and the millennium.

Decommissioning is a very tall order indeed under such circumstances, especially as there are still questions about how the British government will enact much of the Patten report, a key ingredient behind IRA support for the peace process. There is also every likelihood that decommissioning will completely dominate the new executive, making concerted political action impossible.

Ironically, David Trimble's best bet will be to work the institutions as fast and hard as he can, in order to make an IRA move on arms possible.

Having wedded his future to their determinations, any refusal to work the new institutions, particularly the cross-Border ones, could seal his fate.

There is now a huge onus on the two governments to move as expeditiously as possible to implement the provisions of the Good Friday agreement fully. Promising to enact the Patten Commission recommendations, in particular, will be a vital part of this strategy.

The major fear must be that, even in the best possible circumstances, the IRA will make no decision rather than a negative or positive one. There will be powerful voices within the movement warning that handing over arms and risking a split is far too dangerous, given the lack of time to evaluate the new institutions.

THE IRA, too, has its bureaucratic structure in which decisions can be reached in agonisingly slow fashion and where no decision is often the easiest outcome, as some have learnt to their cost in the past.

The primary instinct in the IRA is to avoid a split at all costs. David Trimble's future survival will pale into insignificance beside that reality.

Is it do-able in the new time frame? If the governments and parties commit fully to the implementation of the agreement and the primacy of politics is quickly established, then there is a chance. The onus on the Sinn Fein leadership is enormous, and they know they have an exceedingly tough task ahead if they decide to press forward with very little time to accomplish it.

Perhaps Gen de Chastelain will "emerge sooty-faced" - to use one Irish Government official's characterisation - to say to a press conference that an act of decommissioning has occurred sometime early in the new year. If he does, then the republican leadership will have surpassed any of its accomplishments up to now, given this time frame.

There is no shortage of enemies on either side waiting in the long grass to bushwhack them if they fail. Ironically, David Trimble must now become their biggest cheerleader, just the latest example of how decommissioning has warped normal political discourse in Northern Ireland.