Destroying the Belfast Agreement would weaken the North's union with Britain faster than any other action, according to the Ulster Unionist leader, Mr David Trimble.
Speaking to a largely hostile audience at a UUP youth wing conference at the weekend, Mr Trimble castigated 40 delegates for passing a motion which called on the party to end all links with Sinn Fein and exclude the party from an executive.
The UUP and Sinn Fein will meet again at Castle Buildings today under the chairmanship of Senator George Mitchell as part of the review of the implementation of the Belfast Agreement aimed at solving the impasse over decommissioning and the formation of an executive.
Mr Trimble stressed on Saturday that reaching an accommodation with Sinn Fein was now "a political reality" for unionists, but he reiterated the party stance on decommissioning.
"The party policy is and will remain quite simply no guns, no government. I'm setting that straight at the outset so we don't get any confusion and no one gets upset or worried."
"No guns, no government" was the same as saying guns before government, said Mr Trimble, and an inclusive executive would only be formed if Sinn Fein delivered on its obligations under the agreement.
Speaking as Mr Trimble entered the conference, the dissident UUP Assembly member, Mr Peter Weir, criticised the leadership for negotiating with Sinn Fein and said a "fudge" by the UUP on the decommissioning issue would not be tolerable or acceptable.
In a dynamic speech, Mr Trimble defended the agreement as the best approach available to unionism.
"The fact that agreement was made and endorsed by the electorate changes the situation. It makes it impossible to reopen it or rewrite it. It's no good saying I would have preferred a different agreement because that is no longer an option."
He said there was no way back to "the approach of immobilism", and people intent on wrecking the agreement were making a serious mistake. Political progress could only be achieved if alignments were created that all elements of the political spectrum in the North could buy into, including Sinn Fein.
"If you think they can produce a situation that's going to be better for unionism you are wrong. If unionism destroys the agreement do you think that any element of society in the British Isles, whether Northern Ireland, Great Britain or even the Republic of Ireland, is going to do business with you? That would destroy the union faster than any other course of action you can think of."
Ninety-five per cent of Northern Catholics supported the agreement and 25 per cent of this electorate would vote to remain part of Britain in a referendum on the principle of consent, he said.
"What will that block of opinion think if the agreement is simply destroyed? You will not then be able to make the same calculations you made hitherto with regard to future referenda." At the end of his opening speech at the conference, in Bangor, Co Down, the former UUP leader, Lord Molyneaux, received a standing ovation when he warned the youth wing: "Face the facts. This time they are going for the jugular. This could be our last chance," he added.
In an apparent attack on Mr Trimble he said the "enforced" agreement contained obscure phrases which meant what the two governments chose them to. "No intelligent person can regard it as either durable or workable."