Sinn Féin's Martin McGuinness has said the northern institutions are unlikely to remain in place until assembly elections due next May.
Mr McGuiness told RTÉ News that he believed David Trimble had decided he did not want to be in government with Sinn Féin ahead of those elections.
He said he believed the Ulster Unionist leader had taken a strategic decision to act as a paler shade of Ian Paisley and to pursue an anti-Sinn Féin agenda.
Mr McGuinness said the Good Friday Agreement was the only show in town and there was no doubt about Sinn Féin's commitment to the peace process.
Meanwhile, David Trimble has said British Prime Minister Tony Blair must prove he is the guardian of the peace process by bringing pressure to bear on Republican paramilitaries to implement an unambiguous cease-fire.
Mr Blair or the Northern Secretary, John Reid, are expected to make a statement on the peace process before the Commons rise for the summer recess on Wednesday.
Speaking on the anniversary of Bloody Friday, Mr Trimble said the IRA's apology last week for civilians killed in the bombings did not reflect the actions of Republicans over the last couple of months, when he said they were involved in violence in Belfast.
Mr Trimble said he hoped Mr Blair would clarify what his government would do in the statement this week.