There is every chance the Ulster Unionists could withdraw from the current multi-party talks, party leader David Trimble has warned.

The former first minister said the British and Irish Governments must take action to unpick "the private backroom deal over cross border bodies".

After an hour-long meeting with Secretary of State Paul Murphy, Mr Trimble said amending legislation should be introduced in the Irish Parliament.

The two governments have - behind our backs - created a mechanism to allow decisions to be taken Sir Reg Empey UUP

Without that, he warned, the Good Friday Agreement would "be placed in mortal danger".

"Let's see what happens over the next few days to resolve this matter," said Mr Trimble.

"Let me make it absolutely clear it has to be resolved satisfactorily and I hope the present staff in the Northern Ireland Office will have learned something from the way they have been duped on this occasion."

Ulster Unionist Sir Reg Empey said "a treaty" had been agreed by both governments "without our knowledge and consent".

"The two governments have - behind our backs - created a mechanism to allow decisions to be taken, decisions which should be taken with the consent of the unionist members of the assembly and executive.

"That consent has been set aside."

He said the arrangement had the potential to become joint sovereignty over the specific areas concerned.

In a statement, a spokesman for the Northern Ireland Office said its intention was absolutely clear - "the care and maintenance of the North-South Ministerial Council during suspension.

'Stood down'

Meanwhile, Sinn Fein president Gerry Adams is in Washington for a series of meetings with senior US politicians.

During the three day visit, he will hold talks with President Bush's special adviser on Northern Ireland, Richard Haass.

Speaking ahead of the visit, Mr Adams said his primary focus would be on the need to reinstate the devolved institutions as soon as possible.

The move comes as a senior Ulster Unionist said the US administration was gearing up for a deal to allow for the restoration of devolution.

Richard Haass met UUP MP David Burnside

Northern Ireland's power-sharing institutions were suspended on 14 October following allegations of continuing IRA activity.

South Antrim MP David Burnside said he believed the deal would involve an undertaking from republicans that the IRA would be stood down.

Mr Burnside, who held talks with Richard Haass at the weekend, said a commitment to disarming from the IRA would not be enough to persuade unionists to return to the power-sharing administration with republicans.

He insisted there was no prospect of unionists sharing power with Sinn Fein because of allegations linking the IRA to spying at the Northern Ireland Office, a break-in a Castlereagh police complex in Belfast and training left wing rebels in Colombia.

"If he (Mr Haass) thinks there is any chance of unionists considering that with events in Colombia, Castlereagh and the spy ring, he is wrong.

"I can see no circumstances in the foreseeable future where the UUP can contemplate going into an executive with Sinn Fein."

The anti-Agreement MP also told Mr Haass that unionists would almost certainly leave the Northern Ireland Policing Board if the British Government passed legislation to allow former terrorist prisoners to join the district policing partnerships.

No progress

Northern Ireland Secretary Paul Murphy and Irish Foreign Minister Brian Cowen have been co-hosting multi-party talks but so far there is no sign of progress.

The Ulster Unionists have insisted they will not return to power-sharing with Sinn Fein until there is absolute certainty the IRA will cease all paramilitary activity.

Following the collapse of power-sharing at Stormont, current legislation dictates that the British and Irish Governments must review the implementation of the Good Friday Agreement on which devolution was based.

But unless some common ground can be found between the parties on how to proceed, there is no mechanism for reinstating the power-sharing executive.

Both the governments have stressed that there will be no re-negotiation of the Good Friday Agreement.