The Ulster Unionist leader, Mr David Trimble, is likely to come under pressure to increase sanctions against Sinn Fein at a meeting of his party executive. The meeting takes place in Belfast today.
Anti-agreement members are expected to argue that the ban on Sinn Fein ministers attending North-South ministerial council meetings is not enough and tougher measures need to be adopted if the stalemate on decommissioning continues.
The 110-strong executive is expected to spend several hours discussing future strategy. Mr Trimble will brief his colleagues on the latest behind-the-scenes negotiations involving the two governments and the political parties.
Anti-agreement Ulster Unionist Party members last night said they wanted the party leadership to agree to a progressive withdrawal from government if the Provisional IRA does not adhere to a timetable on decommissioning.
The UUP pro-agreement wing has so far resisted such a move. It is understood attempts will be made to produce a compromise proposal. Mr Trimble yesterday told Sinn Fein ministers Mr Martin McGuinness and Ms Bairbre de Brun that he would continue to ban them from cross-Border ministerial meetings.
His initial ban was declared illegal by the High Court last week. However, in a letter to the two ministers yesterday, Mr Trimble said an opening in the judgment allowed him to keep out any minister failing to implement the Belfast Agreement.
Sinn Fein had failed to bring about IRA decommissioning and was guilty of undermining public confidence in the agreement, he said. He challenged the party to say what it had to done to help achieve decommissioning, why it had failed, and what it planned to do in future.
Until these questions were answered, he could not be satisfied Sinn Fein ministers were upholding the agreement and were therefore suitable persons to represent the Executive.
Ms de Brun, rejected his claims and accused him of threatening the agreement. "David Trimble's refusal to nominate myself and Martin McGuinness to the North-South Ministerial Council is outside the terms of the Good Friday agreement and a breach of his pledge of office.
"The High Court judgment confirmed this and ruled his actions unlawful. That remains the position. His letter is a threadbare attempt to tailor his reasons to suit the judgment and clearly does not stand up to scrutiny."
Sinn Fein Assembly member Mr Gerry Kelly accused Mr Trimble of widening the gap between the UUP and his party. The UUP leader appeared to be afraid of entering the Westminster election while in government with Sinn Fein, he said.
Intense efforts will continue over the weekend to break the political deadlock. Both Irish and British government officials are involved in intensive talks with the pro-agreement parties.
Sources said the negotiations were at a crucial stage. The Northern Secretary, Dr John Reid, yesterday advised the North's political leaders to do or say nothing over coming days which would jeopardise the talks process.