A survey of UUP politicians has revealed near-universal opposition to compromise on the issue of decommissioning.
UUP members of the Northern Ireland Assembly were asked by the BBC's On The Record programme whether the new executive could be formed before IRA weapons and explosives were surrendered.
Of the 19 who replied, 17 said decommissioning was both an obligation and a precondition to the formation of the new executive.
All 19 said the executive could not be formed on the strength of a commitment to decommission at a later date.
The First Minister, Mr David Trimble, has meanwhile called on Sinn Fein to give a pledge that the IRA will disarm completely by May 2000, the deadline laid down in the Good Friday agreement for arms decommissioning.
He has said such a promise is "what is necessary to save this agreement". The survey results indicate that such a pledge would not be enough to satisfy his party's members, lending credence to speculation that pressing ahead on this basis may split the UUP.
Asked whether such a promise could be made, Sinn Fein's chief negotiator, Mr Martin McGuinness, said: "There is an absolute pledge from Sinn Fein to work in good faith with the decommissioning body . . . I am giving a guarantee that I will use all the influence I have to bring about full decommissioning within the time frame . . .
"The only test that Sinn Fein had to pass to get into the executive was to get the required mandate," he added. Mr McGuinness also called on Mr Trimble to "take courage in his hands" and press ahead.