The "absolute" midnight deadline came and went without a deal. The various parties left still without agreement four hours later. The talks will resume for a final push at 1200 BST.

Prime Minister Tony Blair and his Irish counterpart Bertie Ahern are staying in Belfast, suggesting the faint hope a breakthrough remains.

But after an 18-hour session with few breaks it became clear no compromise agreement acceptable to both sides was close.

Denis Murray in Stormont: "The two prime ministers believe they can still do it"

The Ulster Unionists maintain they will not sit with the political wing of the IRA, Sinn Fein, in Northern Ireland's government without a start to arms decommissioning by the republican movement.

Sinn Fein continues to insist it cannot guarantee this and points out it was not in the Good Friday Agreement, which demands disarmament by all groups by May 2000.

Gerry Adams: "Prior decommissioning not achievable"

In the final hours of the marathon session, US President Bill Clinton had a number of phone conversations with Mr Blair and other party leaders.

There was also a last-minute decision to publish a report by General John De Chastelain on the readiness of paramilitary groups to disarm. It is now in the hands of Mr Blair and Mr Ahern, who may seek to use it as a central plank of any agreement.

Sinn Fein President Gerry Adams said he was disappointed the talks had broken up.

Gerry Adams: "People need to take their courage in their hands"

"The talks were adjourned because David Trimble sent his team without consultation with any of the other parties," he said.

"I think all this has made the situation more difficult than it was and that's certainly a disappointment for us, and it's a disappointment I'm sure, for everyone else."

'Decommissioning timetable'

He said proposals put forward by Sinn Fein - the nature of which he refused to reveal - had been rejected by the unionists and he was disappointed by the passing of another deadline.

It is thought Mr Adams' party suggested a timetable for decommissioning before May 2000 - but conditional on the unionists accepting them into an executive in charge of the new administration.

David Ervine says Sinn Fein "have crossed the Rubicon in some ways".

David Trimble, leader of the Ulster Unionist Party and Northern Ireland's first minister in waiting, insists weapons must be handed over at the same time legislative powers are transferred from London to Belfast.

Sinn Fein, the SDLP and the Irish Government have all accused Mr Trimble of stalling and at the same time risk losing what they consider to be the best offer available from the republican leadership.

David Trimble: No concrete proposals

The Progressive Unionist Party's David Ervine said there was disquiet a deadline had been created, but they had been told some "issues" were on the table.

He said: "We have still got a set of talks. They have gone past the deadline, but there is all to play for."

Just prior to the midnight deadline, Mr Trimble and Sinn Fein President Gerry Adams had a face-to-face meeting with the two prime ministers. Both emerged downbeat.

John de Chastelain: His report could form a key plank of a deal

Mr Trimble said he had been prepared to "move forward together" with the republicans but his side had not received any concrete proposals.

He said suggestions an executive could be formed with decommissioning starting three to six months down the line was "simply not in the real world".