Northern Ireland's parties will struggle to get back into power-sharing if the British government suspends the institutions, Sinn Féin warned today.
As the Belfast Agreement hit its worst crisis over allegations that republicans carried out an espionage operation in Belfast, Sinn Féin's Mr Martin McGuinness warned Mr Blair against suspending the institutions to save the peace process.
He said: "The way I look at this is if the institutions come down, I think the task of getting them back up again will be much more difficult than previously.
"In fact it will be much more difficult because we know, because they tell us, the rejectionist wing of the Ulster Unionist Party who are now in the ascendancy are not going to enter into power sharing institutions in the North [of Ireland] or any institutions of an all-Ireland nature," he said.
Mr McGuinness accused unionists of focusing solely "on things they hope the IRA are doing rather than on the attacks which are taking place on the nationalist, Catholic community".
Sinn Féin continues to protest the innocence of a party official remanded in custody on Sunday night on five charges of possessing documents of use to terrorists.
Mr Blair is expected to meet Ulster Unionist leader Mr Trimble at Downing Street. Mr Trimble is likely to tell Mr Blair if the British government did not move to expel Sinn Féin this week from the Northern Ireland government for terrorist activity, his party would.
Ulster Unionist sources said the British government would have until Thursday to act.
The Rev Ian Paisley's Democratic Unionists are expected to begin a unionist walkout from the executive over the allegations against Sinn Féin, pulling out two of its ministers - Mr Peter Robinson and Mr Nigel Dodds.
Mr Blair is expected to meet with Sinn Féin leaders at Downing Street on Thursday when he is expected to challenge them to explain the charges against their head of administration at Stormont, Mr Denis Donaldson.
The Taoiseach, Mr Ahern, and SDLP leader Mark Durkan are due to go the Downing Street tomorrow for crisis talks.
PA