Senator George Mitchell returns to Stormont this afternoon amid guarded optimism that Sinn Fein and the Ulster Unionist Party could do a deal to break the decommissioning/ devolution logjam.
Both Sinn Fein and the UUP agree that the discussions this week are crucial to the deadlock being broken.
There appears to be a growing consensus that any new formula must see Sinn Fein in government, based on some form of acceptable assurance that IRA decommissioning will follow. It is unclear, however, how such an assurance would square with the republican insistence that any movement on IRA weapons must be at least perceived as voluntary.
Talks sources were extremely concerned that any comments or detail about a possible solution appearing in the media could wreck this final phase of the Mitchell review.
But they confirmed that the recent weeks of secret and difficult negotiations in Belfast and London at last appear to be yielding results. "My understanding is that while the deal is not yet done, the mood in both the Ulster Unionist and Sinn Fein camps is more upbeat," said one informed source.
He warned, however, that it could be another long week of negotiations before agreement is reached, and that there were still enough pitfalls that could destroy the chances of a successful outcome to the review.
Senator Mitchell is due to arrive at Stormont about 2 p.m. today, and is expected to speedily engage in talks with the parties, chiefly Sinn Fein and the UUP, led respectively by Mr Gerry Adams and Mr David Trimble.
Senator Mitchell has said that following his talks with President Clinton, the Taoiseach, Mr Ahern, the British Prime Minister, Mr Blair, and Gen. John de Chastelain of the decommissioning body, he will produce his own report this week.
It is unclear whether this will be an outline of the outstanding problems, Mr Mitchell's own take-it-or leave set of proposals detailing what he believes is the best method to end the impasse, or a blueprint he knows will be acceptable.
One Dublin observer said he expected Senator Mitchell to strike quickly, perhaps producing his report as early as tomorrow.
"I think we will know the lie of the land in the next 48 hours," he said last night.
"The problem is that unionists want definition on arms, while republicans need matters to be a little vague. My sense is that Sinn Fein and the Ulster Unionists were given the weekend by Senator Mitchell to figure out whether they can finally crack this problem."
"Whatever the solution it has to be acceptable to both sides and sellable to both sides," he said.
Sinn Fein held an ardchomhairle meeting in Dublin on Saturday, where the party's ruling executive was briefed by Mr Adams on developments in the Mitchell review.
Afterwards, Mr Caoimhghin O Caolain TD said republicans were determined that the review would succeed.
"We are going in to make it work, and to see the Good Friday agreement implemented in full," he said. "The Good Friday agreement remains the best chance of a peaceful future".
Equally, the UUP MP, Mr Ken Maginnis, said his party was seeking a successful resolution. "We are desperately trying to find a way to secure long-term political stability," he said.
