Sinn Fein's chief negotiator, Mr Martin McGuinness, has said that the Provisional IRA will not accept decommissioning as a precondition to his party's entry into a power-sharing executive in the North.
With multi-party talks on the way forward due to resume next week, Mr McGuinness said: "I don't believe the IRA are going to jump to any ultimatum issued by David Trimble or those elements within the British military establishment."
He alluded to the dangers of a split in the republican movement. "The history of republicanism from time immemorial shows they are not going to bend the knee to the demands of elements of the British military establishment or unionism, particularly if their assessment is that this is seen as an issue which can divide republicanism on this island."
Under the terms of an Anglo-Irish declaration drafted by the Taoiseach and the British Prime Minister, Mr Blair, at Hills borough Castle last week, the Provisionals must begin a decommissioning process before Sinn Fein's two nominated ministers can enter the executive.
As part of a "collective act of reconciliation", weapons would have to be "put beyond use on a voluntary basis" and in a manner to be verified by Gen John de Chastelain, the head of the disarmament commission.
It is not yet clear if Mr Blair and Mr Ahern will return to the North for the resumed talks next Tuesday, or wait until they are fairly certain of a deal. A decision on the venue - either Hillsborough Castle or Parliament Buildings, Stormont - has also to be taken.
Mr McGuinness said there was republican resistance to the demands for decommissioning. He said it was "very, very dangerous" for the Hillsborough declaration to make decommissioning a precondition.
Sinn Fein would be seeking clarification on what was meant by "a collective act of reconciliation" and "some arms put beyond use". If the British and Irish governments had changed their view from the Belfast Agreement which made it clear decommissioning was not a precondition for entry to an executive, "then we are all in very serious difficulty", he added.
He said Sinn Fein would go into next week's talks to try to find a resolution but he added: "I am working on the basis that there is no prospect whatsoever for the IRA to decommission anything as a precondition to Sinn Fein's participation in an executive.
"I don't believe the IRA are going to jump to any ultimatum or demand issued either by David Trimble or those elements within the British military establishment who have hung unto this issue in a very unrealistic and unrealisable way over the course of the last four years."
The Ulster Unionist Assembly group will meet on Monday before the multi-party negotiations on the Hillsborough declaration resume. The 27-member group will hold discussions on tactics. An Ulster Unionist Assembly member, Mr Billy Armstrong, yesterday expressed his opposition to key aspects of the Hillsborough declaration and said it was unacceptable in its present form.
Sir Reg Empey, another UUP member, said his party would be looking for clarification of parts of the declaration.
"There is lots of language that is almost unintelligible. It is for us to tease out the meaning of these phrases. I regret very much that it is written in this Anglo-Irish language which the general public do not understand," he said.