Ulster Unionist Party (UUP) MPs and Assembly members are to meet today ahead of a "significant" announcement about powersharing in Northern Ireland.
Unionists have threatened to exclude Sinn Fein from the ministerial Executive after revelations that the IRA still exists. A unionist walk out from the Stormont body is another option.
It follows remarks by the Police Service of Northern Ireland (PSNI) that the paramilitary group still exists but is not engaged in terrorism.
The PSNI also said some of its members were involved in the murder of father-of-nine Kevin McGuigan in Belfast two weeks ago but it was not sanctioned at a senior level.
Ireland's Justice Minister Frances Fitzgerald has ordered a "fresh assessment" of the activities of the Provisional IRA by Irish police.
The PSNI analysis - almost 20 years after the Provisional IRA's last ceasefire and a decade on from decommissioning its weapons - has triggered another political controversy at Stormont.
Unionists have threatened a bid to exclude Sinn Fein from the devolved powersharing Executive. Sinn Fein said there is no basis for the threats.
But Northern Ireland Secretary Theresa Villiers said she remained satisfied that all parties in the Assembly remained committed to peace.
Sinn Fein leader Gerry Adams said over the weekend the IRA has "gone away".