The DUP stands prepared to bring down Stormont if Sinn Fein is not excluded from the Executive, Secretary of State Theresa Villiers has been warned.
With the sense of political crisis deepening, DUP deputy leader Nigel Dodds has said his party would push for the republican party to be thrown out of the coalition administration if it did not deal with revelations about the involvement of some PIRA members in murder.
Mr Dodds indicated his party would be prepared to bring down the institutions if the issue was not dealt with "very speedily".
He led a party delegation to meet Northern Ireland Secretary Theresa Villiers in Belfast to discuss the political crisis sparked by the shooting of former IRA man Kevin McGuigan and a subsequent assessment by PSNI Chief Constable George Hamilton that the PIRA still exists and some of its members were involved in the killing.
And Mr Dodds said the Secretary of State had also agreed with the assertion that it could not be "business as usual" at Stormont in the current climate.
But, following a meeting with Mrs Villiers yesterday, Mr Dodds said his party still wanted further talks with Prime Minister David Cameron and another meeting with Chief Constable George Hamilton before it would take any action.
"Our interest is ensuring that this matter is dealt with, that Sinn Fein are put under pressure, that they are forced to deal with this matter and that, if they don't, then they are excluded or devolved government does not continue on that basis - that is our priority, that is our objective," he added.
"We will continue to monitor the situation in terms of what the Chief Constable will say to us and what the Government and others say to us but there is no reason at all, as things stand at the moment, why there should not be the exclusion of Sinn Fein on the basis of what the Chief Constable has already said."
Mr Dodds said a lot could happen before the next scheduled meeting of the Executive, which is not for another two weeks, on Thursday, September 10.
But referring to the UUP move to give up its Executive seat rather than sit with Sinn Fein, Mr Dodds added: "We have made it very clear that we will not be found wanting when it comes to making sure this matter is addressed."
The SDLP, which also met Mrs Villiers yesterday, said the UUP withdrawal - expected to be endorsed by its ruling executive tomorrow - was "premature".
Leader Alasdair McDonnell said his party would not be involved in "knee-jerk" gestures in backing a motion to exclude Sinn Fein, as more evidence of IRA involvement was still required.
An Alliance delegation also met Mrs Villiers and put a number of proposals it said could bring stability to government here.
Meanwhile, it has emerged that Sinn Fein could gain an extra ministerial seat as a result of Ulster Unionists pulling out of the Executive.
The DUP will have first choice in replacing the UUP's Danny Kennedy as Regional Development Minister - and Peter Robinson could do so to prevent Sinn Fein gaining from the current crisis engulfing the Assembly.
But if the DUP refuses the choice it then goes to Sinn Fein, a senior Ulster Unionist has conceded.
And the source also told the Belfast Telegraph it was not a "foregone conclusion" that the party's Executive would ratify leader Mike Nesbitt's decision to withdraw from the power-sharing administration.
The source said there was also no mechanism for the UUP to move into a formal opposition, because there was no agreement with the other parties.
The senior UUP figure, who did not want to be named, said: "This does not come at no cost to us and there are many who are uneasy about how this will end up, but I do think the leader's strategy will win a majority."