The Ulster Unionist leader, Mr David Trimble, has warned that current attempts to salvage the Belfast Agreement could fail because of the paramilitaries' refusal to decommission their weapons.
His comments came as British and Irish officials finalise details of a package designed to resolve issues of policing, decommissioning, demilitarisation and the stability of the institutions.
The parties expect the text to be sent to them this week for consideration.
"My prime objective is to see this agreement implemented, and fully implemented, and that is the sole reason behind what I have been doing over the last few months," Mr Trimble said.
"But there are obviously other possibilities in the situation if it turns out we cannot implement it fully because the paramilitaries won't abide by their own obligations underneath it."
The UUP leader, who resigned as the North's First Minister on July 1st in protest over the lack of movement on IRA weapons, was speaking to BBC News 24 in an interview to be screened tonight.
A UUP negotiator, Mr Jeffrey Donaldson, yesterday reacted angrily to speculation that an indemnity law would be among the Governments' proposals. The move would introduce a general amnesty for all unsolved killings linked to the North's violence.
Mr Donaldson stressed there was no provision in the Belfast Agreement for an amnesty, and unionist MPs in Westminster would oppose any such legislation.
"If Tony Blair and his Government delivers this concession as a part of a package then it may as well be the final nail in the coffin of the appeasement process, because I do not believe any self-respecting unionist would buy into such a deal," he said.
An NIO spokesman declined to comment on the speculation and said that no specific timetable had emerged for the presentation of the package to the parties.
Speaking after a meeting of the Sinn Fein executive in Dublin on Saturday to discuss the negotiations, the party chairman, Mr Mitchel McLaughlin, said they hoped for a productive outcome. However, he reiterated Sinn Fein's demand that the package not diverge from the agreement.
"In terms of policing, there is a very, very specific remit for an accountable and representative policing service that all can join," he said. "If the British government cannot deliver on that, there have to be serious questions about their commitment."
The deadline for agreement had been set as August 12th, six weeks following Mr Trimble's resignation. However it now appears the British government may avoid suspending the Assembly or calling fresh election due to a legislative "quirk".