Northern Ireland leader David Trimble says Britain must expel the Sinn Fein party from the province's government or the power-sharing coalition will collapse. Mr. Trimble discussed the crisis with British Prime Minister Tony Blair Tuesday.

Mr. Trimble emerged from his hour-long meeting with Mr. Blair saying Britain must act against Sinn Fein by next Tuesday or Northern Ireland's government will fall apart.

He said Sinn Fein should no longer hold cabinet posts in the power-sharing coalition amid allegations the party ran a spying operation on behalf of the Irish Republican Army.

Mr. Trimble said he will resign if Mr. Blair does not expel Sinn Fein. And he laid out his conditions for staying on as leader of the Northern Ireland government. "Where the issue of a private army had been completely resolved. Where we had a situation where there was no continuing illegal activity, and that the private army, the IRA, had been disbanded," he said.

Mr. Blair told reporters ahead of the meeting that the benefits of Northern Ireland's Good Friday peace agreement, signed in 1998, are on the line in the current crisis. "The Good Friday agreement, the peace process, offers the best chance of a successful future, if it can be made to work. But it can only be made to work on the basis that everyone accepts the full principles of that agreement, and that is equality and justice on the one side and an end to any form of violence and terrorism on the other," Mr. Blair said.

Mr. Blair's Northern Ireland secretary, John Reid, came out after the talks with Mr. Trimble and described the situation as "very difficult and grave."

Mr. Reid said no decision will be reached on how to deal with the crisis until after Mr. Blair meets Wednesday with Irish Prime Minister Bertie Ahern and Sinn Fein leader Gerry Adams.

The Northern Ireland government is made up of four parties representing the unionist and republican movements. Unionists want Northern Ireland to remain part of Britain, while republicans favor merger with the Irish republic.