The North's First Minister, Mr David Trimble, said the political deadlock over decommissioning and the establishment of the executive would be overcome "sooner or later".
Mr Trimble was speaking as the parties held further discussions at Stormont yesterday as part of Senator George Mitchell's review of the implementation of the Belfast Agreement. It is understood that the talks will continue tomorrow.
The participants yesterday refused to divulge details of the discussions, but said Senator Mitchell had not yet presented them with any document containing his own proposals.
Mr Trimble said the decommissioning issue had still to be resolved, but all the parties were "addressing it seriously". He said he hoped the negotiations would succeed but it was too soon to make any prediction.
The SDLP deputy leader, Mr Seamus Mallon, said the next few days would be absolutely crucial. "If we don't get agreement there is going to be great political uncertainty," he said.
Mr Mallon stressed that it was up to local politicians to take hard decisions to reach a deal. There was a good working atmosphere but ambience was no substitute for agreement. The Alliance leader, Mr Sean Neeson, said: "D-day is fast approaching, and while some politicians fear moving forward, the alternative is too awful to contemplate."
Mr Peter Mandelson welcomed a group of 52 Protestant clergy to Stormont yesterday. The ministers said they were there to urge the politicians to find a way forward.
The Northern Secretary told the group of Presbyterian, Church of Ireland, Methodist and Evangelical ministers there was no alternative to the Belfast Agreement.
"If we didn't have the Good Friday agreement, if it didn't exist, you would have to invent it," he said. "And if we scrapped it, we would end up with exactly the same agreement because it is the only thing that accommodates everyone's points of view.
"It's a rounded agreement that provides a way forward. In every respect, in every element, it just takes us forward in stages which are perfect if only people would unlock the door and go in and allow us to implement it. "Everywhere I have been this week, every single person has said to me `Please God, let them do it this week', and I think that is the sentiment of everyone in Northern Ireland and I can understand why. The sooner we do this and strike a deal on the implementation of the agreement the quicker we will start enjoying the benefits of the Good Friday agreement, and that's what everyone wants."
When asked whether he expected the current talks to conclude this weekend, Mr Mandelson replied: "They are still talking, and George Mitchell is there. He is keeping them together. They are very serious and that is encouraging."
The clergymen were also greeted by the Sinn Fein president, Mr Gerry Adams, who thanked them for their prayers and said his party would do its best to make the deal work.