Mr David Trimble seems set for a collision with London, Dublin and the SDLP. The issue is his proposal for a rule change designed to make it easier to exclude Sinn Féin from ministerial office at Stormont.
The UUP leader and Northern Ireland's First Minister wants the British government to set aside the existing provisions for exclusion of parties or individuals on the basis of a cross-community vote in the Assembly and to take the power for itself.
Mr Trimble revealed his plan at a Westminster press conference yesterday intended to put pressure on the British Prime Minister, Mr Tony Blair, ahead of emergency talks between the two governments and the pro-agreement parties in Belfast.
Flanked by his Westminster chief whip, Mr Roy Beggs MP, and by his leading dissident, Mr Jeffrey Donaldson MP, Mr Trimble listed the pledges made by Mr Blair during the 1998 referendum campaign and told the Prime Minister it was "time to deliver" on his promise to support changes to the exclusion mechanisms proposed in the Belfast Agreement should they prove ineffective.
Mr Blair made that promise in his famous letter to Mr Trimble as the Belfast Agreement was concluded in April 1998. At yesterday's press conference, Mr Donaldson insisted the proposed change be made and should not be subject to any form of "veto" by the Irish Government.
Challenged about this, Mr Trimble recalled that London had acted unilaterally in the matter of the suspension of the Assembly and Executive in February 2000. However, Mr Trimble later appeared to accept that he would need the agreement of the Taoiseach, Mr Ahern.
But the UUP leader's apparent confidence that he might win the Taoiseach's agreement surprised Irish sources, who offered little prospect of Dublin consenting to reopen the exclusion issue or any of the terms of the agreement, save with the consent of all the parties.
Downing Street also seemed unimpressed. The Prime Minister's official spokesman said: "We are concentrating on steps to make sure that the agreement is implemented in full, including an end to all paramilitary actions, rather than changing the agreement at this stage."
Mr Trimble said he was not accusing Mr Blair of any insincerity when he made his 1998 pledges about Britain's requirements for the end of paramilitarism and the terms for early prisoner releases. But he would ask Mr Blair "is your conscience clear" given an outcome very different to that which he had promised.