Q&A: Assembly crisis

Unionist ministers are resigning from the Northern Ireland executive. BBC News Online explains why.

What led to this decision?

The resignation of the ministers comes after months of stand-off over the final implementation of the Good Friday Agreement. For unionists it all comes down to the IRA's failure to decommission its weapons. Last week the Ulster Unionists put forward a motion to exclude Sinn Fein from the assembly executive over the matter.

The party resents that it is still sharing power with Sinn Fein without movement on guns.

Did the motion have any chance of success?

No. In order to succeed, the motion required cross-community support.

So even though it had unionist backing, it required a majority of nationalists in the assembly to agree.

The SDLP could have provided that majority of nationalists. But the party made it clear it would not support any action which it believed would damage the institution.

So what has been David Trimble's decision?

The UUP's ministers are resigning from the executive from midnight Thursday because there has not been a start to decommissioning.

Mr Trimble's strategy has been to crank up pressure on republicans. But he also said that he timetabled the party's moves towards the resignations so that there could be a "soft landing" and orderly transfer of power to the Northern Ireland Office to allow a review.

Following the resignation of a minister, there is a seven day nomination period for the UUP to put forward new ministers before the institutions collapse.

Mr Trimble could reinstate his ministers during this period of grace if there were movement from the IRA.

So what would make him renominate the ministers?

Actual IRA decommissioning in the first instance, or at least a watertight plan and evidence that it is beginning. There are strong indications that talks are continuing behind the scenes involving the parties, London, Dublin and possibly officials in Washington. Sinn Fein has dropped heavy hints that the IRA may be preparing a move far more significant than its ceasefire, should it judge the conditions to be right.

Those conditions, according to republicans, focus on David Trimble withdrawing his threat to collapse the institutions and movement by the UK government on other issues, principally a scaling down of the military presence.

Mr Trimble has refused to withdraw the resignations, saying that republicans have strung along Northern Ireland before and it is now time for action.

What will the British Government do?

The government has a number of options. The secretary of state could step in and suspend the institutions before, or immediately after, the Ulster Unionists withdraw or resign.

In this case, John Reid would have to go for an open-ended suspension and review.

This is believed to be the preferred UUP option - the soft landing that Mr Trimble referred to.

If Dr Reid does allow the institutions to collapse, he is obliged under law to dissolve the assembly and call elections. The SDLP and Sinn Fein are wholly opposed to suspension saying that the institutions should not be held hostage by one party.

If there was IRA decommissioning during the next few weeks would it make any difference to the unionists?

This is the question that republicans have grappled with.

Republicans say they are suspicious that even if weapons were put beyond use to the satisfaction of the arms commission, led by General John de Chastelain, and the British and Irish Governments, that unionists would still find reason to block power-sharing.

David Trimble says that weapons must be put beyond use to the satisfaction of the de Chastelain Commission - and that and once this happens, he is prepared to continue power-sharing.

The question is: Can he face down elements in his party that will remain dissatisfied?