A promise by republicans to disarm would not be sufficient to ensure Ulster Unionist acceptance of the two governments' proposals published yesterday, according to the UUP leader, Mr David Trimble.
"We have had enough promises - they were not acted upon. We have moved beyond that. We will wait to see if there is any serious movement on decommissioning.
"By that I mean something actually happening that comes within the statutory remit of Gen De Chastelain's commission. If that happens, well and good; if not, then we move into a deeper crisis and I don't want to speculate on what will happen at that stage."
Mr Trimble said that the current crisis in the peace process would only be resolved by republicans fulfilling obligations. "In the absence of decommissioning there will be no progress, and consequently no Ulster Unionist will be able to offer himself for election as First Minister."
Following Mr Trimble's resignation as First Minister at the beginning of last month, the Assembly is approaching an August 12th deadline for electing a First Minister.
Mr Trimble said: "There can't be a moral vacuum at the heart of this. We are not legitimising terrorism. It's not all right to be in government by day and out engaged in other activities by night."
Commenting on the two governments' package of proposals dealing with decommissioning, policing, normalisation, and the stability of the institutions, Mr Trimble said: "If we don't see any action on decommissioning, then the rest of the paper is virtually meaningless."
He continued: "On May 6th, 2000, the republican movement promised to put their weapons completely and verifiably beyond use. Fourteen months later they have not even told the Independent International Commission on Decommissioning what those words might mean," he said.
"Everything else is moving forward. Everything else is either fully implemented or well on the way to being so. The one thing on which there has been no movement has been with regard to weapons."
The proposal to review the implementation of the Patten report in 12 months' time was "a glimmer of light", he believed.
"I think that will show up the limitations of Patten and give us an opportunity to start repairing some of the damage done by Patten."
Proposals for investigations into the deaths of RUC officers Chief Supt Harry Breen and Supt Bob Buchanan, Lord and Lady Gibson, and Billy Wright were also welcomed, as was a review of the Parades Commission.
"Of course we know, even though the government puts a good face on it, that the Parades Commission has been an abysmal failure. I think we have to get back to the point that we made when that commission was instituted - that the legislation was misconceived, and that we need to get back and look at that issue again."
Anti-agreement Ulster Unionist MP Mr Jeffrey Donaldson said that in the absence of decommissioning he thought the party would be looking at the withdrawal of not only the First Minister but all the UUP ministers from the North's Executive.
Mr Donaldon's fellow MP, Mr David Burnside, said he hoped his party would reach agreement to reject the proposals by Monday's deadline.
"This overall package is not, in my opinion, acceptable to the broad unionist family and I will put my view as a Member of Parliament before next Monday to the party leader David Trimble and I would hope that we will be united on Monday and reject these proposals," he told BBC Radio 4's The World At One programme yesterday.
The full text of the two governments' proposals is available on the Irish Times website at: www.ireland.com