The UK Government is set to begin the process of suspending the Northern Ireland Assembly and re-imposing direct rule from Westminster.

The fledgling Northern Ireland Assembly and its power-sharing executive will be suspended on Friday 11 February if the IRA does not commit to arms decommissioning.

Northern Ireland Secretary Peter Mandelson said on Friday that if he had no assurances decommissioning was to happen, he would put the eight-week-old Northern Ireland government on hold in seven days.

However, he added that it was not too late for paramilitaries to co-operate and he believed in Sinn Fein's commitment to peace.

"It could be they are great actors, it could be that they have all perfectly mastered a single script. It could be they are all leading us by the nose," he said at the Institute of Irish Studies in Liverpool.

"But I believe they have been sincere in their commitment to the Good Friday Agreement and their desire to get the IRA to decommission, but they have been unsuccessful to date."

The legislation to suspend the Assembly has been published at Westminster. The nine-page Bill is expected to be passed next week, unless there is a last-minute breakthrough.

Decommissioning crisis

However, Sinn Fein has warned that the republican movement may not distinguish between suspension and collapse.

Speaking as the emergency legislation went before Westminster, the party's president Gerry Adams accused Peter Mandelson of "disgraceful" behaviour.

David Trimble, the assembly's First Minister and leader of the Ulster Unionists, is meeting his party to discuss his threat to withdraw from the eight-week old body.

He argues that he cannot sit in government with Sinn Fein because the IRA has failed to begin decommissioning.

That threat, already contained in a post-dated letter to his party, came after General John de Chastelain's independent report found there had been no movement towards paramilitary decommissioning.

The proposed suspension of the assembly is designed to prevent Mr Trimble from stepping down - it is feared that would bring the collapse of the Good Friday Agreement.

As talks continued in Belfast, Prime Minister Tony Blair made it clear that movement had to come from the IRA.

"The unionists have got to know that the people they're sitting down with are no longer wedded to the ballot box and the gun," he said.

US President Bill Clinton has added his voice to calls to preserve the peace process, saying it was vital all sides honoured their agreements.

'Intensive talks'

But Mr Adams said a number of people were continuing to walk a tightrope despite the best efforts of the republican movement to find an answer.

"Peter Mandelson's remarks yesterday were disgraceful. We were told he would put out a holding statement," he said.

"Myself and others in leadership have been in intensive discussions with the Irish government and British government and in regular contact with both and with other parties and with the IRA.

"That is far beyond my responsibility, far beyond my obligations and at the time when we were actually talking to the IRA - what does Peter Mandelson do? He accused them of betraying the process."