Ulster Unionist Party leader Mr David Trimble was this evening preparing for a major showdown with his anti-Agreement critics which could decide the future of unionism.
Mr Trimble is expected to defeat a motion by anti-Agreement MP Mr Jeffrey Donaldson at tomorrow's meeting of the party's ruling council - but there are fears that it could split the party in two.
Mr Donaldson, MP for Lagan Valley, who has urged the council's 900 members to reject the British and Irish governments' Joint Declaration, said it was a "defining moment for unionism".
He has dismissed a compromise amendment from Mr Trimble which while, refusing to endorse the Joint Declaration, does not reject it outright.
The Joint Declaration, published by the two governments after multi-party negotiations, includes plans for a scaling down of the British military presence in Northern Ireland, a scheme to allow fugitive terror suspects to return, and the creation of a sanctions body to punish parties in default of the Belfast Agreement.
These moves would be implemented in return for the IRA giving up its terror campaign for good and getting rid of its weapons.
In a six-point amendment, Mr Trimble condemned plans for an amnesty for exiled terrorist suspects and called for the retention of the home battalions of the Royal Irish Regiment.
The amendment makes clear that the UUP does not endorse the Joint Declaration and that no consideration would be given to a return to devolution until the ruling council had the opportunity to consider the words and actions of republicans.
But Mr Donaldson's dismissal of his leader's resolution appears to have destroyed any chance of a compromise between the two UUP camps.
In a thinly-veiled attack on the leadership, Mr Donaldson said: "The days of constructive ambiguity are at an end. We cannot fudge this issue of the Joint Declaration."